Patent Description:
Known displays for aerosol-generating devices employ a light source within the device to illuminate a window of the display by backlighting the window with a light wave generated by the light source. It is known to impart different colours to the illuminated window with the light source to provide a user with an indication of the status of the device. For example, it is known to impart one or more desired colours to the backlit window by the use of a light source emitting light of one or more specific wavelengths corresponding to one or more desired colours. However, there is a problem with known displays in that the material of the window may impart an undesired change in the colour of the light from the light source as it passes through the window. This can be a particular problem when using a dead-front display, because the window of a dead-front display attenuates certain wavelengths of light. Such attenuation is commonly used to ensure that the colour of the window, when the display is in a non-operational state, corresponds to the colour of the device of which the display forms part. However, when the window is backlit by a light source within the device, this attenuation characteristic may impart an undesired tint to the illuminated window.

There is therefore a need for a display providing improved control of colour.

As used herein, the term "light" refers to emissions of electromagnetic radiation which are in the visible range of the electromagnetic spectrum, which is generally understood to encompass wavelengths in a range of about <NUM> to about <NUM>. White light is formed of a broad spectrum of different wavelengths of light, each wavelength corresponding to a different colour.

As used herein, the term "nano-structures" refers to structural entities whose major dimension is sized less than <NUM>. The terms "nano-cavities" and "nano-particles" as recited below are to be interpreted accordingly.

As used herein, the term "quantum dot" refers to a semiconductor nano-particle that confines charge carriers in three dimensions.

<CIT> relates to a lighting device having a light converter, the light converter comprising semiconductor quantum dots. <CIT> relates to methods and apparatus for a transparent display using scattering nanoparticles. <NPL> relates to the use of surface plasmon resonance to enhance the efficiency of a conventional LED.

<CIT> discloses a similar aerosol-generating device. Furthermore, <CIT>, <NPL>", <NPL>, <CIT>, <CIT>, <NPL>", <CIT>, <CIT> and <NPL>" disclose similar displays comprising nano-photonic materials.

According to a first aspect, there is provided a display for an aerosol-generating device, the display comprising:.

The nano-photonic material is responsive to the incident light wave such that the incident light wave triggers or energises the nano-photonic material to generate and radiate therefrom light comprising the desired at least one predetermined wavelength. As the predetermined wavelength will correspond to an associated colour in the visible part of the electromagnetic spectrum, the use of a nano-photonic material extending over the front surface of the window provides an enhanced ability to tune the colour of the window of the display when backlit, and to compensate for any attenuation of wavelength component(s) of the incident light wave caused by the underlying window material.

Preferably, the nano-photonic material comprises a plurality of nano-structures, the nano-structures comprising either or a combination of nano-cavities and nano-particles, the nano-structures being arranged, sized or formed so as to generate and radiate therefrom light comprising the at least one predetermined wavelength in response to a light wave backlighting the window and being incident on the nano-photonic material.

Silicon-based materials and gallium nitride (GaN) are examples of suitable materials for use in forming the nano-photonic material. For example, the nano-photonic material may comprise a substrate of a silicon-based material or gallium nitride (GaN), with nano-particles arranged within the substrate. Metal oxides and indium gallium nitride (InGaN) are examples of suitable materials for the nano-particles. However, these specific materials are given only as examples. The nano-particles may conveniently take the form of quantum dots; for example, an arrangement of quantum dots may be provided within a substrate of the nano-photonic material.

Photolithography may be used to form the nano-photonic material. By way of example, if the nano-photonic material is to include both nano-cavities and nano-particles, a substrate material containing an arrangement of nano-particles may be used as a starting material. Alternatively, no nano-particles may be present in the substrate starting material. In either case, photolithography may be used to etch a predetermined arrangement of nano-cavities into the substrate starting material.

Preferably, the nano-structures are arranged, sized or formed such that the generation and radiation therefrom of light comprising the at least one predetermined wavelength is conditional upon a parameter of the incident light wave having a given value or range of values. This conditionality assists in enhancing control of under what circumstances the display radiates certain wavelengths (and thereby colours) of light, i.e. at the least one predetermined wavelength having its corresponding colour(s). Conveniently, the parameter is selected from one or more of a wavelength, a frequency and an amplitude of the incident light wave.

Advantageously, the nano-structures may comprise nano-particles arranged, sized or formed within the nano-photonic material such that individual nano-particles or groups of the nano-particles are drivable by the incident light wave to plasmonically resonate so as to generate and radiate light comprising the at least one predetermined wavelength. In this preferred aspect, the incident light wave serves to energise the nano-photonic material to induce plasmonic resonance of the individual nano-particles or the groups of nano-particles, resulting in the nano-particles emitting light at one or more desired wavelengths, i.e. at the at least one predetermined wavelength. The wavelength of light emitted by the nano-particles or groups of nano-particles through plasmonic resonance can be determined (for example, computationally) for a given configuration of nano-photonic material.

Advantageously, the plurality of nano-structures comprise a first group of nano-structures and a second group of nano-structures; the first group configured so as to generate and radiate therefrom light having a first wavelength composition, the first wavelength composition comprising at least one first predetermined wavelength; the second group configured so as to generate and radiate therefrom light having a second wavelength composition, the second wavelength composition comprising at least one second predetermined wavelength; in which the first and second wavelength compositions differ from each other. The configuration of the nano-structures in first and second groups to provide light having different wavelength compositions provides improved control of the wavelength and colour of light generated and radiated by different parts of the nano-photonic material. The first wavelength composition may consist of a single wavelength; the same may apply to the second wavelength composition. Alternatively, the first wavelength composition may consist of two or more wavelengths; again, the same may apply to the second wavelength composition.

Preferably, the first group of nano-structures comprises a first plurality of nano-particles sized and arranged within the nano-photonic material to plasmonically resonate in response to an incident light wave so as to generate and radiate light therefrom having the first wavelength composition. Similarly, the second group of nano-structures may preferably comprise a second plurality of nano-particles sized and arranged within the nano-photonic material to plasmonically resonate in response to an incident light wave so as to generate and radiate light therefrom having the second wavelength composition.

Conveniently, the first and second groups of nano-structures are arranged, sized or formed such that: the generation and radiation of light having the first wavelength composition by the first group is conditional upon a parameter of the incident light wave having a first given value or range of values; and the generation and radiation of light having the second wavelength composition by the second group is conditional upon the parameter of the incident light wave having a second given value or range of values; in which the first and second given values and range of values differ from each other. This feature provides improved control over the wavelength and colour of light radiated by different parts of the nano-photonic material. The display may further comprise a light source in optical communication with the window for backlighting the window with a light wave to fall incident on the nano-photonic material, the light source operable to switch between: the parameter of the incident light wave having the first given value or range of values; and the parameter of the incident light wave having the second given value or range of values. The parameter is conveniently selected from one or more of a wavelength, a frequency and an amplitude of the incident light wave. It can therefore be seen that changes in the incident light wave generated by the light source can be used to control the wavelength and corresponding colour of the light which is generated and radiated by the nano-photonic material.

For the various forms of nano-photonic material described above, the nano-photonic material may comprise a crystalline lattice defining a network of nano-cavities, in which individual nano-particles or groups of nano-particles are contained within one or more regions defined within the crystalline lattice between the nano-cavities. Such an arrangement of individual nano-particles or groups of nano-particles within a crystalline lattice is particularly suitable for being driven by an incident light wave to plasmonically resonate so as to generate and radiate light at desired wavelengths, i.e. at the at least one predetermined wavelength. Individual nano-cavities of the lattice may be spaced apart from each other in a predetermined pattern or repeating arrangement. However, in one or more regions within the crystalline lattice between adjacent nano-cavities, there may be a discontinuity in the predetermined pattern or repeating arrangement. The locating of individual nano-particles or groups of nano-particles in such discontinuity regions has been found particularly suitable for the generating and radiating of light by plasmonic resonance, with individual nano-particles or groups of nano-particles located in such regions being sensitive to being driven by an incident light wave to plasmonically resonate as outlined above. The wavelength emitted by individual nano-particles or groups of nano-particles located in such regions may be determined computationally based on the size and location of the regions, the size and location of the nano-cavities, the material from which the lattice and the nano-particles are made, and the size and location of the nano-particles. Different groups of nano-particles within the crystalline lattice may, in response to an incident light wave, generate and radiate therefrom light having different respective wavelength compositions. This difference in wavelength composition may be influenced by any one or more of i) the specific region in which the different groups of nano-particles are located, ii) the size and number of nano-particles in the different groups, and iii) the use of nano-particles formed of different materials in the different groups.

Advantageously, the nano-particles have a diameter in a range of between <NUM> to <NUM>. The nano-cavities may have a diameter in a range of between <NUM> to <NUM>.

Preferably, the display further comprises a light source in optical communication with the window for backlighting the window with a light wave to fall incident on the nano-photonic material. Light emitting diodes (LEDs) have been found particularly suitable as light sources, having good energy efficiency. However, other light sources capable of backlighting the window may be similarly suitable. The light source is conveniently adapted to backlight the window with a light wave comprising a spectrum of different wavelengths of light. Advantageously, the light source is adapted to switch between emitting light waves having different compositions of wavelengths. By way of example, in a first mode of operation the light source may be configured to emit a light wave comprised of one or more wavelengths which provide a red colour to the light (i.e. with wavelengths generally in the range of <NUM> to <NUM>); in a second mode of operation the light source may be configured to emit a light wave comprised of one or more wavelengths which provide a green colour to the light (i.e. with wavelengths generally in the range of <NUM> to <NUM>), and in a third mode of operation the light source may be configured to emit a light wave comprised of one or more wavelengths which provide a blue colour to the light (i.e. with wavelengths generally in the range of <NUM>-<NUM>).

The nano-photonic material is conveniently provided as a layer of nano-photonic material extending over the front surface of the window. Preferably, the layer of nano-photonic material is provided as a layer of a polymer-based film.

The display may be a dead-front display in which the window comprises material configured to attenuate light at one or more predetermined attenuation wavelengths. Preferably, the at least one predetermined wavelength is within <NUM> of at least one of the one or more predetermined attenuation wavelengths. Accordingly, the light generated and radiated by the nano-photonic material may be of a wavelength and colour composition very similar to those wavelengths and colours of light which would be attenuated by the material of the window of the dead-front display.

In a second aspect, there is provided a display for an aerosol-generating device, the display comprising:.

As described above, the nano-photonic material preferably comprises a plurality of nano-structures, the nano-structures comprising either or a combination of nano-cavities and nano-particles. The presence of such nano-cavities or nano-particles can be said to have an effect of enhancing the intensity of the colour associated with the at least one predetermined wavelength of light. The nano-structures may be arranged, sized or formed to, in response to a light wave comprising the at least one predetermined wavelength backlighting the window and being incident on the nano-photonic material, increase the amplitude of the at least one predetermined wavelength and emit therefrom a light wave comprising the at least one predetermined wavelength with the increased amplitude.

Advantageously, the plurality of nano-structures are arranged and sized to, in response to a light wave comprising the at least one predetermined wavelength backlighting the window and being incident on the nano-photonic material, diffract the incident light wave. Preferably, the plurality of nano-structures comprise at least a first diffraction site and a second diffraction site, the first and second diffraction sites arranged and sized to each diffract the at least one predetermined wavelength of the incident light wave by a predetermined amount, such that the diffracted predetermined wavelength of light from the first diffraction site and the diffracted predetermined wavelength of light from the second diffraction site intersect with and reinforce each other. So, the first and second diffraction sites can be thought of as functioning like the slits of a diffraction grating. Where the nano-structures comprise either or a combination of nano-cavities and nano-particles, individual ones of the nano-cavities and/or nano-particles may each individually serve as separate diffraction sites.

Preferably, the nano-photonic material is comprised of a crystalline lattice defining a network of nano-cavities. In such a crystalline lattice of nano-cavities, the nano-cavities may be arranged and sized so as to behave like the slits of a diffraction grating in response to an incident light wave, with the incident light wave passing through and being diffracted by individual ones of the nano-cavities. In a further preferred embodiment, individual nano-particles or clusters of nano-particles may be provided in the crystalline lattice between the nano-cavities. Similarly, in such a crystalline lattice containing both nano-particles and nano-cavities, the nano-particles and the nano-cavities may be arranged and sized to each individually behave like the slits of a diffraction grating in response to an incident light wave, so as to diffract the incident light wave.

As described above for the first aspect, silicon-based materials and gallium nitride (GaN) are examples of suitable materials for use in forming the nano-photonic material. For example, the nano-photonic material may comprise a substrate of a silicon-based material or gallium nitride (GaN), with nano-particles arranged within the substrate. Metal-oxides and indium gallium nitride (InGaN) are examples of suitable materials for the nano-particles. However, these specific materials are given only as examples. The nano-particles may conveniently take the form of quantum dots; for example, an arrangement of quantum dots may be provided within a substrate of the nano-photonic material.

As described above for the first aspect, photolithography may be used to form the nano-photonic material. By way of example, if the nano-photonic material is to include both nano-cavities and nano-particles, a substrate material containing an arrangement of nano-particles may be used as a starting material. Alternatively, no nano-particles may be present in the substrate starting material. In either case, photolithography may be used to etch a predetermined arrangement of nano-cavities into the substrate starting material.

As described above for the first aspect, the nano-particles preferably have a diameter in a range of between <NUM> to <NUM>. The nano-cavities preferably have a diameter in a range of between <NUM> to <NUM>.

The display may further comprise a light source in optical communication with the window for generating a light wave to backlight the window, the light wave comprising the at least one predetermined wavelength. As described above for the first aspect, light emitting diodes (LEDs) have been found particularly suitable as light sources, having good energy efficiency. However, other light sources capable of backlighting the window may be similarly suitable.

Preferably, the display is a dead-front display in which the window comprises a material configured to attenuate light at one or more predetermined attenuation wavelengths, in which the at least one predetermined wavelength is within <NUM> of the one or more predetermined attenuation wavelengths. So, the nano-photonic material is able to compensate for attenuation in amplitude of the predetermined wavelength by the window material, by acting to boost the intensity of the predetermined wavelength of light. This behaviour may be beneficial in compensating or offsetting, at least in part, the attenuating effect of a dead-front display for certain wavelengths of light during operation of the display.

As described above for the first aspect, the nano-photonic material is conveniently provided as a layer of nano-photonic material extending over the front surface of the window. Preferably, the layer of nano-photonic material is provided as a layer of a polymer-based film.

In a third aspect, there may be provided a display for an aerosol-generating device, the display comprising a notification window; a nano-photonic material extending over a front surface of the window; in which the nano-photonic material is configured in accordance with both of the first and second aspects outlined above.

Advantageously, there is provided an aerosol-generating device comprising the display as outlined in any of the preceding paragraphs in relation to the first three aspects, in which the aerosol-generating device further comprises: a housing, wherein the display is integrated into the housing; and a light source enclosed within the housing and in optical communication with the window for backlighting the window with a light wave to fall incident on the nano-photonic material. Preferably, the window is a notification window in which a colour of the window (as visible to a user of the aerosol-generating device), in response to the light source backlighting the window provides the user with a notification of the status of the device. The colour of the notification window may provide an indication as to whether the aerosol-generating device (or a component part thereof) has reached or exceeded a design operating temperature. For example, a blue colour for the backlit window may be indicative of a heating element of the aerosol-generating device not yet having reached a design operating temperature, whereas a green colour for the backlit window may be indicative of the heating element having attained the design operating temperature, whereas a red colour may be indicative of the heating element having exceeded the design operating temperature. Of course, it is understood that in other embodiments, there may be a different association between a given colour of the backlit notification window and a given status of the aerosol-generating device.

Conveniently, the aerosol-generating device is a smoking article for generating aerosol for inhalation by a user. Alternatively, the aerosol-generating device is configured to cooperate with a smoking article so as to induce the smoking article to generate aerosol for inhalation by a user. The aerosol-generating device is preferably elongate in form and sized so as to be suitable for being held between the thumb and fingers of a user. The aerosol-generating device is preferably cylindrical in cross-section. Conveniently, the housing of the device is adapted to contain an aerosol-forming substrate. A power source and a heating element are also preferably contained within the housing of the device, the power source configured to provide electrical power to the heating element such that the heating element is able to apply heat to the aerosol-forming substrate so as to generate a vapour from the substrate. It is preferred that this same power source also provides electrical power to any light source provided in the device used to backlight the window of the display. The aerosol-forming substrate may conveniently be provided as part of a replaceable cartridge. Preferably, the aerosol-forming substrate is provided in a solid form, although the aerosol-forming substrate may alternatively be provided in liquid form. The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise plant-based material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise homogenised tobacco material. The aerosol-forming substrate may comprise a non-tobacco-containing material. The aerosol-forming substrate may comprise homogenised plant-based material.

Examples will now be further described with reference to the figures, in which:.

<FIG> shows an aerosol-generating device <NUM>. The aerosol-generating device <NUM> is elongate and generally cylindrical in cross-section, with a housing <NUM> having an upper part 2a and a lower part 2b. The parts 2a, 2b of the housing mate with each other at a diagonal interface <NUM>. A display <NUM> is integrated into the housing <NUM>. The display includes four notification windows <NUM>, <NUM>, <NUM>, <NUM>. The notification windows <NUM>, <NUM>, <NUM>, <NUM> define icons of different shapes. The aerosol-generating device <NUM> is sized in length and diameter so as to be suitable for being held between the thumb and fingers of a user. The aerosol-generating device <NUM> shown in <FIG> is a smoking article for generating smoke for inhalation by a user. Although not shown in the figures, a replaceable cartridge containing aerosol-forming substrate and an electrically-powered heating element are enclosed within the housing <NUM> of the device <NUM>, with the heating element operable to apply heat to the aerosol-forming substrate to generate an inhalable aerosol therefrom, for inhaling from an opening in the upper part 2a of the housing <NUM> of the device <NUM>. This inhalable aerosol is represented by the array of dashed lines in <FIG> emanating from the upper part 2a of the housing <NUM>.

<FIG> shows a cross-sectional view of the aerosol-generating device <NUM> along line A-A of <FIG>, corresponding to the location of the lowermost notification window <NUM> of the display <NUM>. An accompanying detail view localised on the notification window <NUM> is also provided in <FIG>. A light source <NUM> is located within a cavity <NUM> provided inside the housing <NUM>. For the embodiment shown, the light source <NUM> is a light-emitting diode (LED). The light source <NUM> is mounted on a printed circuit board <NUM> which contains wiring and control circuitry (not shown) for controlling the operation of the light source. The printed circuit board <NUM> is electrically coupled to a power source <NUM> for providing power to the light source <NUM>. The power source <NUM> not only provides power to the printed circuit board <NUM>, the light source <NUM> and other components mounted on the printed circuit board, but also provides power to the heating element (not shown) used to apply heat to the aerosol-forming substrate (also not shown). For the embodiment shown in <FIG>, the power source <NUM> is a rechargeable battery. The cavity <NUM> is arranged such that the light source <NUM> is in optical communication with a back-facing surface <NUM> of the notification window <NUM>. In use, the light source <NUM> illuminates the back-facing surface <NUM> of the notification window <NUM> with a light wave to thereby backlight the window for viewing by a user of the device <NUM>. The cavity <NUM> is arranged such that a light wave from the light source <NUM> backlights the window <NUM> without illuminating any of the other three notification windows <NUM>, <NUM>, <NUM> of the display <NUM>. The printed circuit board <NUM> extends for the length of the display <NUM>. Three additional light sources (not shown) are mounted on the printed circuit board <NUM> and are located within respective cavities (also not shown) for backlighting each of the remaining three notification windows <NUM>, <NUM>, <NUM>. The configuration of the light source <NUM> and the notification window <NUM> is indicative of the configuration of the notification windows <NUM>, <NUM>, <NUM> and their own respective light sources.

For the aerosol-generating device <NUM>, the display <NUM> is a dead-front display, in which each of the windows <NUM>, <NUM>, <NUM>, <NUM> appear tinted when viewed from outside of the device, so as to correspond in colour to the housing <NUM> when their respective light sources (for example, light source <NUM> for window <NUM>) are inactive. The window <NUM> is made of a polymer configured to attenuate light at one or more predetermined attenuation wavelengths, thereby imparting a tint to the window <NUM>. A layer of nano-photonic material <NUM> overlies a front-facing surface <NUM> of the window <NUM> (see <FIG>).

<FIG> shows a schematic representation of a first embodiment of the layer of nano-photonic material <NUM> overlying the front-facing surface <NUM> of the window <NUM>. The layer of nano-photonic material <NUM> is provided as a layer of a polymer-based film. The layer of nano-photonic material <NUM> is formed of a crystalline lattice of gallium nitride (GaN) defining a network of nano-cavities <NUM>. The nano-cavities <NUM> are spaced apart from each other in a predetermined pattern or repeating arrangement. However, the lattice is fabricated so as to define discontinuities in the predetermined pattern or arrangement of nano-cavities <NUM>. These discontinuities are located in regions 562a to 562f of the crystalline lattice. The discontinuities in regions 562a to 562c define a triangular pattern, as do the discontinuities in regions 562d to 562f. For the embodiment shown in <FIG>, each discontinuity region 562a to 562f contains a group of nano-particles <NUM> in the form of quantum dots formed of indium gallium nitride (InGaN). As can be seen from <FIG>, the nano-photonic material <NUM> has been fabricated to provide clusters 564a, 564b of the groups of nano-particles <NUM>. For the embodiment shown in <FIG>, each cluster 564a, 564b consists of three groups of nano-particles <NUM> arranged in a triangular configuration. The six groups of nano-particles <NUM> (three per cluster 564a, 564b) are located in the six discontinuity regions 562a to 562f of the crystalline lattice. The nano-cavities <NUM> are each sized to have a diameter in a range of between <NUM> to <NUM>. The nano-particles <NUM> are sized to have diameters in a range of between <NUM> to <NUM>.

The behaviour of the nano-photonic material <NUM> overlying the front-facing surface <NUM> of the notification window <NUM> for the embodiment of <FIG> is discussed in response to the window being backlit by a light wave generated by light source <NUM>. The light source <NUM> is configured to generate first and second incident light waves Wi1 and Wi2 at different points in time, dependent on and according to instructions provided by the control circuitry provided on the printed circuit board <NUM>. For the embodiment shown and described in <FIG>, the first and second incident light waves Wi1 and Wi2 have distinct wavelength compositions. For the illustrated embodiment, the first incident light wave Wi1 is composed of "m" constituent wavelengths to provide a wavelength composition of λi1. <NUM>, λi<NUM>. m ; and the second incident light wave Wi2 is composed of "n" constituent wavelengths to provide a wavelength composition of λi2. <NUM>, λi2. The wavelength composition of the first incident light wave Wi1 is different to that the second incident light wave Wi2. In an alternative embodiment, the first and second incident light waves Wi1 and Wi2 may each instead consist of a single wavelength, with the wavelength of the first incident light wave Wi1 being different to that of the second incident light wave Wi2.

When the light source generates first incident light wave Wi1, the light wave Wi1 first passes through the window <NUM> to fall incident on the layer of nano-photonic material <NUM>. On entering the nano-photonic material <NUM>, the light wave Wi1 has the effect of driving or energising the clusters 564a, 564b of the groups of nano-particles <NUM> to plasmonically resonate. For the example of <FIG>, the wavelength composition λi1. <NUM>, λi1. m of the light wave Wi1 generated by light source <NUM> is selected to not include any of one or more predetermined attenuation wavelengths of the window material <NUM>. This helps to ensure that the light wave Wi1, when falling incident upon the layer of nano-photonic material <NUM>, after having passed between the back-facing and front-facing surfaces <NUM>, <NUM> of the window <NUM>, retains sufficient amplitude and energy to drive each of the clusters 564a, 564a of the groups of nano-particles <NUM> to plasmonically resonate. For the example shown in <FIG>, the arrangement and size of the clusters 564a, 564b and their respective nano-particles <NUM> is such that each cluster 564a, 564b generates and radiates an output light wave Wo1 having an output wavelength λo1 corresponding to a desired or predetermined colour of light. Accordingly, to a person viewing the window <NUM> of the display <NUM> when backlit by the light source <NUM>, the window appears to be illuminated with a colour corresponding to the output wavelength λo1.

When the light source <NUM> is switched, by virtue of instructions provided by the control circuitry of the printed circuit board <NUM>, to generate the second light wave Wi2 having the second wavelength composition λi2. <NUM>, λi2. n, the light wave Wi2 passes through the window <NUM> to fall incident upon the layer of nano-photonic material <NUM>. As for light wave Wi1, light wave Wi2 also has the effect of driving or energising the clusters 564a, 564b of the groups of nano-particles <NUM> to plasmonically resonate. Again, the wavelength composition λi2. <NUM>, λi2. n of the light wave Wi2 generated by the light source <NUM> is selected to not include any of one or more predetermined attenuation wavelengths of the window material <NUM>, so as to ensure that the light wave Wi2 retains sufficient amplitude and energy to drive the clusters 564a, 564b to plasmonically resonate. The arrangement, size and material of the clusters 564a, 564b of nano-particles <NUM> is such that each cluster 564a, 564b generates and radiates an output light wave Wo2 having an output wavelength λo2 corresponding to a desired or predetermined colour of light. The output wavelength λo2 of output light wave Wo2 is different to the output wavelength λo1 of output light wave Wo1. So, the light waves Wi1, Wi2 with their different wavelength compositions (λi1. <NUM>, λi1. <NUM>, λi2. n) drive the clusters 564a, 564a to each generate and radiate different output light waves Wo1, Wo2 consisting of different respective output wavelengths λo1, λo2. The different output wavelengths λo1, λo2 correspond to different colours of light. So, a person viewing the window <NUM> of the display <NUM> when backlit with light wave Wi1 having wavelength composition λi1. <NUM>, λi1. m will see the window appear illuminated with a different colour compared to when the window <NUM> is backlit with light wave Wi2 having wavelength composition λi2. <NUM>, λi2. The different colours can be indicative of the status of the aerosol-generating device at a given time. For example, an output wavelength λo1 of about <NUM> (corresponding generally to a blue colour of light) may be indicative of the heating element of the aerosol-generating device <NUM> not yet having reached its design operating temperature, whereas an output wavelength of λo2 of about <NUM> (corresponding generally to a green colour of light) may be indicative of the heating element having attained its design operating temperature. Of course in other embodiments, the clusters 564a, 564b of nano-particles <NUM> may be arranged, sized or formed of a material such that they generate and radiate light at an output wavelength corresponding to different colours.

<FIG> shows a schematic representation of a second embodiment of the layer of nano-photonic material <NUM>' overlying the front-facing surface <NUM> of the window <NUM>. The layer of nano-photonic material <NUM>' is formed of a crystalline lattice defining a network of nano-cavities <NUM>'. The nano-cavities <NUM>' are spaced apart from each other in a predetermined pattern or repeating arrangement. In common with the embodiment of <FIG>, the lattice is fabricated so as to define discontinuities in the predetermined pattern or arrangement of nano-cavities <NUM>'. These discontinuities are located in regions 562a' to 562e' of the crystalline lattice. The discontinuities in regions 562a' to 562c' define a triangular pattern, whereas the discontinuities in regions 562d' to 562e' define a linear pattern. Each discontinuity region 562a' to 562e' contains a group of nano-particles <NUM>' in the form of quantum dots. As can be seen from <FIG>, the nano-photonic material <NUM>' has been fabricated to provide clusters 564a', 564b' of the groups of nano-particles <NUM>'. For the embodiment of <FIG>, cluster 564a' consists of three groups of nano-particles <NUM>' in a triangular arrangement and cluster 564b' consists of two groups of nano-particles <NUM>' in a linear arrangement. The five groups of nano-particles <NUM>' are located in the five discontinuity regions 562a' to 562e'. As for the embodiment of <FIG>, the nano-cavities <NUM>' are each sized to have a diameter in a range of between <NUM> to <NUM>, and the nano-particles <NUM>' sized to have diameters in a range of between <NUM> to <NUM>. However, the nano-particles in cluster 564a' are formed of a material differing in composition from that of the nano-particles in cluster 564b'. As explained below, the use of different materials for the nano-particles <NUM>' of the different clusters 564a', 564b' results in the nano-particles <NUM>' of the different clusters 564a', 564b' responding differently to two different incident light waves, with the differing response being dependent on differences in one or more parameters between two such incident light waves.

The behaviour of the nano-photonic material <NUM>' overlying the front-facing surface <NUM> of the notification window <NUM> for the embodiment of <FIG> is discussed in response to the window being backlit by a light wave generated by light source <NUM>. The light source <NUM> is configured to generate first and second light waves Wi1' and Wi2', at different points in time, dependent on and according to instructions provided by the control circuitry provided on the printed circuit board <NUM>. For the embodiment described, the incident light waves Wi1' and Wi2', have distinct wavelength compositions. For the illustrated embodiment, the first incident light wave Wi1' is composed of "m" constituent wavelengths to provide a wavelength composition of λi1. <NUM>, λi1'. m; and the second incident light wave Wi2' is composed of "n" constituent wavelengths to provide a wavelength composition of λi2'. <NUM>, λi2'. The wavelength composition of the first incident light wave Wi1' is different to that the second incident light wave Wi2'. In an alternative embodiment, the first and second incident light waves Wi1' and Wi2' may each instead consist of a single wavelength, with the wavelength of the first incident light wave Wi1' being different to that of the second incident light wave Wi2'.

When the light source generates first incident light wave Wi1', the light wave Wi1' first passes through the window <NUM> to fall incident on the layer of nano-photonic material <NUM>'. On entering the nano-photonic material <NUM>', the light wave Wi1' drives and energises the cluster 564a' of nano-particles <NUM> to plasmonically resonate. The arrangement, size and material of the cluster 564a' and its respective nano-particles <NUM>' result in the cluster 564a' generating and radiating an output light wave Wo1' having an output wavelength λo1' corresponding to a desired or predetermined colour of light. However, the different material used for the nano-particles <NUM>' of cluster 564b' is such that the nano-particles <NUM>' of cluster 564b' are unresponsive to the first incident light wave Wi1' consisting of wavelength composition λi1'. <NUM>, λi1'. m, resulting in no or negligible plasmonic resonance of the nano-particles <NUM>' of cluster 564b'. So, to a person viewing the window <NUM> of the display <NUM> when the window is backlit by light wave Wi1' with wavelength composition λi1'. <NUM>, λi1'. m, the window would appear illuminated with a colour corresponding to the output wavelength λo1' of the light generated and radiated by cluster 564a' only.

When the light source <NUM> is switched, by virtue of instructions provided on the control circuitry of the printed circuit board <NUM>, to generate the second incident light wave Wi2' having second wavelength composition λi2'. <NUM>, λi2'. n, the light wave Wi2' passes through the window <NUM> to fall incident upon the layer of nano-photonic material <NUM>'. On entering the nano-photonic material <NUM>', the light wave Wi2', drives and energises the cluster 564b' of nano-particles <NUM>' to plasmonically resonate. The arrangement and size of the cluster 564b' and its constituent nano-particles <NUM>' results in the cluster 564b' generating and radiating an output light wave Wo2' having an output wavelength λo2' corresponding to a desired or predetermined colour of light. However, the different material used for the nano-particles <NUM>' of cluster 564a' is such that the nano-particles <NUM>' of cluster 564a' are unresponsive to the second incident light wave Wi2' consisting of wavelength composition λi2'. <NUM>, λi2'. n, resulting in no or negligible plasmonic resonance of the nano-particles <NUM>' of cluster 564a'. So, to a person viewing the window <NUM> of the display <NUM> when the window is backlit by light wave Wi2' with wavelength composition λi2'. <NUM>, λi2'. n, the window would appear illuminated with a colour corresponding to the output wavelength λo2' of the light generated and radiated by cluster 564b' only.

The embodiment of <FIG> illustrates how the use of different materials for the nano-particles <NUM>' of the different clusters 564a', 564b' can result in these different clusters reacting differently to incident light waves Wi1', Wi2', differing in one or more parameters. For the embodiment of <FIG>, the light waves Wi1', Wi2', differ in their wavelength composition. However, in alternative embodiments, the nano-particles of the different clusters 564a', 564b' may instead react differently according to differences in the frequency and/or amplitude of the light waves Wi1', Wi2'. Further, for the embodiment shown in <FIG>, the different arrangement of the clusters 564a' (triangular pattern) and 564b' (linear pattern) also results in each cluster generating and radiating light of different wavelengths.

The output wavelength λo1' of output light wave Wo1' from cluster 564a' is different to the output wavelength λo2' of output light wave Wo2' from cluster 564b'. The different output wavelengths λo1', λo2' correspond to different colours of light.

<FIG> shows a schematic representation of a third embodiment of the layer of nano-photonic material <NUM>" overlying the front-facing surface <NUM> of the window <NUM>. The layer of nano-photonic material <NUM>" is provided as a layer of a polymer-based film. The layer of nano-photonic material <NUM>" is formed of a crystalline lattice of gallium nitride (GaN) defining a network of nano-cavities <NUM>". The nano-cavities <NUM>" are spaced apart from each other in a predetermined pattern or repeating arrangement. In contrast to the embodiments of <FIG> and <FIG>, the lattice for this third embodiment is fabricated to avoid or minimise the presence of discontinuities in the predetermined pattern or arrangement of nano-cavities <NUM>". Nano-particles <NUM>" are dispersed throughout the lattice in a predetermined pattern and spacing, being located between adjacent ones of the nano-cavities <NUM>". The nano-particles <NUM>" are in the form of quantum dots formed of indium gallium nitride (InGaN). The nano-cavities <NUM>" are each sized to have a diameter in a range of between <NUM> to <NUM>. The nano-particles <NUM>" are sized to have diameters in a range of between <NUM> to <NUM>.

The behaviour of the nano-photonic material <NUM>" overlying the front-facing surface <NUM> of the notification window <NUM> for the embodiment of <FIG> is discussed in response to the window being backlit by a light wave generated by light source <NUM>. The light source <NUM> is configured to generate incident light wave Wi, according to instructions provided by control circuitry provided on the printed circuit board <NUM>. For the embodiment shown and described in <FIG>, the incident light wave Wi has a wavelength composition consisting of "p" constituent wavelengths λi. In an alternative embodiment, the incident light wave Wi may instead consist of a single wavelength.

When the light source <NUM> generates incident light wave Wi, the light wave first passes through the window <NUM> to fall incident on the layer of nano-photonic material <NUM>". On entering the nano-photonic material <NUM>", the individual nano-cavities <NUM>" and nano-particles <NUM>" function like the slits of a diffraction grating, to diffract the constituent wavelengths of the incident light wave Wi. The action of the individual nano-cavities <NUM>" and nano-particles <NUM>" in diffracting a specific predetermined wavelength λi. x present in the incident light wave Wi is discussed below with reference to <FIG>. As the incident light wave Wi passes through the nano-photonic material <NUM>", the nano-cavities <NUM>" and nano-particles <NUM>" diffract or deflect the constituent wavelengths present in the incident light wave. Different constituent wavelengths present in the incident light wave Wi are diffracted by different amounts. The diffraction by nano-cavities <NUM>" and nano-particles <NUM>" of the predetermined wavelength component λi. x present in incident light wave Wi into diffracted light waves Wdiff(λi. x)nc and Wdiff(λi. x)np respectively is shown in <FIG>. The diffracted light waves Wdiff(λi. x)nc emanating from different ones of the nano-cavities <NUM>" interfere with each other, with these regions of interference indicated schematically as "R1" in <FIG>. Similarly, the diffracted light waves Wdiff(λi. x)np emanating from different ones of the nano-particles <NUM>" also interfere with each other, with these regions of interference indicated schematically as "R2" in <FIG>. The interference in regions "R1" of the diffracted waves Wdiff(λi. x)nc results in localised increases in amplitude and intensity of light having a colour corresponding to wavelength λi. Similarly, the interference in regions "R2" of the diffracted waves Wdiff(λi. x)np results in localised increases in amplitude and intensity of light having a colour corresponding to wavelength λi. The amount of diffraction for a given wavelength component present in the incident light wave Wi is a function of the size of the individual nano-cavities <NUM>" and nano-particles <NUM>". Further, the interference between different diffracted waves for a given wavelength and the resulting increase in amplitude and intensity is influenced by the spacing between adjacent ones of the nano-cavities <NUM>" and the nano-particles <NUM>". Where the predetermined wavelength λi. x present in the incident light wave Wi corresponds to or is close to (for example, within <NUM>) any of the one or more predetermined attenuation wavelengths of the window material <NUM>, the interference of the diffracted light waves in regions R1 and R2 and corresponding increase in amplitude and intensity can help to offset any initial reduction in amplitude of the predetermined wavelength component λi. x of the incident light wave Wi caused by the attenuating effect of the window material <NUM>.

<FIG> shows a schematic representation of a fourth embodiment of the layer of nano-photonic material <NUM>‴ overlying the front-facing surface <NUM> of the window <NUM>. The layer of nano-photonic material <NUM>‴ is formed of a crystalline lattice of gallium nitride (GaN) defining a network of nano-cavities <NUM>‴. The nano-cavities <NUM>‴ are spaced apart from each other in a predetermined pattern or repeating arrangement. In contrast to the embodiment of <FIG>, no nano-particles are provided within the layer of nano-photonic material <NUM>‴. The nano-cavities <NUM>‴ are each sized to have a diameter in a range of between <NUM> to <NUM>.

The behaviour of the nano-photonic material <NUM>‴ overlying the front-facing surface <NUM> of the notification window <NUM> for the embodiment of <FIG> is discussed in response to the window being backlit by a light wave generated by light source <NUM>. The light source <NUM> is configured to generate incident light wave Wi, according to instructions provided by control circuitry provided on the printed circuit board <NUM>. As for the embodiment shown and described in <FIG>, the incident light wave Wi has a wavelength composition which consisting of "p" constituent wavelengths λi. In an alternative embodiment, the incident light wave Wi may instead consist of a single wavelength.

When the light source <NUM> generates incident light wave Wi, the light wave first passes through the window <NUM> to fall incident on the layer of nano-photonic material <NUM>‴. In a similar manner to the embodiment of <FIG>, on entering the nano-photonic material <NUM>"', the individual nano-cavities <NUM>‴ function like the slits of a diffraction grating to diffract the constituent wavelengths of the incident light wave Wi. The action of the individual nano-cavities <NUM>‴ in diffracting a specific predetermined wavelength λi. x present in the incident light wave Wi is discussed below with reference to <FIG>. As the incident light wave Wi passes through the nano-photonic material <NUM>‴, the nano-cavities <NUM>‴ diffract or deflect the constituent wavelengths present in the incident light wave. Different constituent wavelengths present in the incident light wave Wi are diffracted by different amounts. The diffraction by nano-cavities <NUM>‴ of the predetermined wavelength component λi. x present in the incident light wave Wi into diffracted light waves W'diff(λi. x)nc is shown in <FIG>. The diffracted light waves W'diff(λi. x)nc emanating from different ones of the nano-cavities <NUM>‴ interfere with each other, with these regions of interference indicated schematically as "R3" in <FIG>. The interference in regions "R3" of the diffracted waves W'diff(λi. <NUM>)nc for wavelength λi. <NUM> results in localised increases in amplitude and intensity of light having a colour corresponding to the wavelength λi. The amount of diffraction for a given wavelength component present in the incident light wave Wi is a function of the size of the individual nano-cavities <NUM>‴. Further, the interference in between different diffracted waves for a given wavelength and the resulting change in amplitude and intensity is influenced by the spacing between adjacent ones of the nano-cavities <NUM>‴. Again, where the predetermined wavelength λi. x present in the incident light wave Wi corresponds to or is close to (for example, within <NUM>) of any of the one or more predetermined attenuation wavelengths of the window material <NUM>, the interference of the diffracted light waves in regions R3 and corresponding increase in amplitude and intensity can help to offset any initial reduction in amplitude of the predetermined wavelength component λi. x in the incident light wave Wi caused by the attenuating effect of the window material.

Claim 1:
An aerosol-generating device (<NUM>), the aerosol-generating device comprising:
a display (<NUM>);
a housing (<NUM>); and
a light source (<NUM>) enclosed within the housing;
wherein the display comprises:
a notification window (<NUM>); and the display further characterized by
a nano-photonic material (<NUM>, <NUM>', <NUM>", <NUM>‴) extending over a front surface of the window;
the light source in optical communication with the window for backlighting the window with a light wave to fall incident on the nano-photonic material;
the nano-photonic material configured to, in response to a light wave comprising at least one predetermined wavelength backlighting the window and being incident on the nano-photonic material, increase the amplitude of the at least one predetermined wavelength and emit therefrom a light wave comprising the at least one predetermined wavelength with the increased amplitude.