Apparatus and method of high power nanosecond mode-locked solid state laser

A mode-locked solid state laser apparatus including an optical film, a gain medium crystal, a Fabry-Perot element, a first mirror, a second mirror, a third mirror and an output coupler is disclosed. The optical film is configured to receive a pumping light having a first wavelength incident in a first direction. The gain medium crystal receives the pumping light passing the optical film, and generates an initial laser beam having a second wavelength, wherein the initial laser beam forms a first optical path starting at one end thereof from the gain medium crystal. The Fabry-Perot element is disposed on the other end of the first optical path opposite to the one end, and reflects the initial laser beam along a second optical path having one end thereof starting from the Fabry-Perot element. The first mirror is disposed on the other end of the second optical path opposite to the one end of the second optical path, and reflects the initial laser beam along a third optical path having one end thereof starting from the first mirror.

The application claims the benefit of Taiwan Patent Application No. 108122024, filed on Jun. 24, 2019, at the Taiwan Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.

FIELD OF THE INVENTION

The present invention is related to a solid state apparatus and method, and more particularly to the apparatus and method of high power nanosecond mode-locked solid state laser.

BACKGROUND OF THE INVENTION

Solid state laser systems are commonly used to provide high-power laser sources, and are also well-adapted for constructing mode-locked lasers to generate laser pulses. Please refer toFIG. 1, which is a schematic diagram of a configuration of a solid-state laser resonant cavity known in the art. According toFIG. 1, the resonant cavity10is composed of an optical film11, an optical gain crystal12, a concave mirror13, a mirror14, and an output mirror15. When the pumping light Lpumpenters the optical gain crystal12through the optical film11, the optical gain medium in the crystal can be excited to release an initial laser beam Linihaving a group of wavelengths close to another wavelength λ, along the light path shown in the figure. After zigzagging between the combination of the concave mirror13and the mirror14, the initial laser beam Liniis directed toward the output mirror15via the lowermost light path inFIG. 1. In an appropriate configuration, the output mirror15can reflect the initial laser beam Liniback along the original path, so that the initial laser beam Liniis continuously reflected back and forth along the light path in the figure to form a closed path with the optical film11and the output mirror15at both ends.

Those skilled in the art can appreciate that in such a constantly closed path, there may be many forms of standing waves with specific wavelengths, which may be referred to as various modes. Therefore, the intensity of the initial laser beam Linihaving the specific wavelengths can be continuously increased in the resonant cavity10, along with the pumping light Lpumpcontinuously being injected into the optical gain crystal12.

The film stack151of the output mirror15is a semiconductor saturable absorber mirror (SESAM) for achieving passive mode locking, and the transmittance thereof has an initial value. When the intensity of the initial laser beam Liniexceeds a threshold, the modes of the laser beam inside the cavity will be superimposed in a specific relationship and a pulse will be generated. Meanwhile, the film stack151causes a minimum loss to form a high penetration state, and a pulsed output laser light Lexitis released through the output mirror15.

The laser light pulse generated by the solid-state laser device described above consists of a group of light beams having mode wavelengths close to the wavelength λ, and the width of the wavelength region of the modal distribution shall be controlled for the application. For the purpose of mode selection, a typical way is to arrange a transmitted Fabry-Perot element16in the light path of the resonant cavity10.

The conventional transmitted Fabry-Perot element consists essentially of two mutually parallel and low-reflectivity optical planes (for example, glass with two flat surfaces). When a homogenous light passes through the transmitted Fabry-Perot element, an interference occurs due to multiple reflections of homogenous light in the two optical planes, which produces a periodic modulation in the output spectrum to select the mode type. When the transmitted Fabry-Perot element16in the figure is disposed in the optical path of the resonant cavity10, interference occurs to the initial laser beam Liniin the optical path, the number of modes decreases, and the modes of the initial laser beam Linitend to be concentrated, achieving the effect of mode selection. If one transmitted Fabry-Perot element16is not sufficiently enough, conventionally one may add another transmitted Fabry-Perot element17to the optical path to enhance the efficiency of the mode selection.

According to the abovementioned, in order to arrange the transmitted Fabry-Perot element16/17in the resonant cavity10, complicated optical component alignment processes are required, which are labor intensive and time-consuming. Moreover, the transmitted Fabry-Perot element16/17causes a power loss, so that the power of the output laser light Lexitdecreases. Therefore, how to avoid the above shortcomings but achieve effective mode selection is a technical issue to be resolved.

In order to overcome the drawbacks set forth above in the prior art, a new design for the laser apparatus is required.

SUMMARY OF THE INVENTION

The present invention provides a novel concept for a solid state laser resonant cavity, using a reflected Fabry-Perot element to replace a reflection mirror, which is simple and time-saving without increasing the total number of optical elements in the resonant cavity. The present invention is advantageous over the apparatus according to the prior art, no matter in terms of power performance or mode selection.

In accordance with one aspect of the present invention, a mode-locked solid state laser apparatus including an optical film, a gain medium crystal, a Fabry-Perot element, a first mirror, a second mirror, a third mirror and an output coupler is provided. The optical film is configured to receive a pumping light having a first wavelength incident in a first direction. The gain medium crystal receives the pumping light passing the optical film, and generates an initial laser beam having a second wavelength, wherein the initial laser beam forms a first optical path starting at one end thereof from the gain medium crystal. The Fabry-Perot element is disposed on the other end of the first optical path opposite to the one end, and reflects the initial laser beam along a second optical path having one end thereof starting from the Fabry-Perot element. The first mirror is disposed on the other end of the second optical path opposite to the one end of the second optical path, and reflects the initial laser beam along a third optical path having one end thereof starting from the first mirror. The second mirror is disposed on the other end of the third optical path opposite to the one end of the third optical path, and reflects the initial laser beam along a fourth optical path having one end thereof starting from the second mirror. The third mirror is disposed on the other end of the fourth optical path opposite to the one end of the fourth optical path, and reflects the initial laser beam along a fifth optical path having one end thereof starting from the third mirror. The output coupler is disposed on the other end of the fifth optical path opposite to the one end of the fifth optical path, and reflects the initial laser beam back to the third mirror along the fifth optical path. The optical film has a first relatively high transmittance for a light at the first wavelength and a first relatively high reflectivity for a light at the second wavelength. The Fabry-Perot element includes a first surface and a second surface parallel to the first surface, wherein the first surface is closer to the first mirror when compared to the second surface and has a second relatively high transmittance, and the second surface has a second relatively high reflectivity. The output coupler has an initial transmittance. On a condition when an intensity of the initial laser beam reaches a threshold value, the output coupler has a third relatively high transmittance and allows an output laser pulse to emit out of the laser apparatus.

In accordance with another aspect of the present invention, a mode-locked solid state laser apparatus is disclosed. The mode-locked solid state laser apparatus comprises an optical film, a gain medium crystal, a concave mirror, a Fabry-Perot element and an output coupler. The optical film is configured to receive a pumping light having a first wavelength incident in a first direction. The gain medium crystal receives the pumping light passing the optical film, and generates an initial laser beam having a second wavelength, wherein the initial laser beam forms a first optical path starting at one end thereof from the gain medium crystal. The concave mirror is disposed on the other end of the first optical path opposite to the one end of the first optical path, and reflects the initial laser beam along a second optical path starting at one end thereof from the concave mirror. The Fabry-Perot element is disposed on the other end of the second optical path opposite to the one end thereof, and reflects the initial laser beam back to the concave mirror so as to reflect the initial laser beam by the concave mirror along a third optical path starting at one end thereof from the concave mirror. The Fabry-Perot element includes a first surface and a second surface parallel to the first surface, and the first surface is closer to the concave mirror when compared to the second surface. The output coupler is disposed on the other end of the third optical path opposite to the one end thereof, and reflects the initial laser beam back to the concave mirror along the third optical path.

In accordance with yet another aspect of the present invention, a method for adjusting a pulse width of a solid-state laser pulse is provided. The method comprises steps of: (A) providing a solid state laser device including: an optical film receiving a pumping light having a first wavelength incident in a first direction; a gain medium crystal, receiving the pumping light passing the optical film, and generating an initial laser beam having a second wavelength, wherein the initial laser beam forms a first optical path starting at one end thereof from the gain medium crystal; a concave mirror, disposed on the other end of the first optical path opposite to the one end thereof, and reflecting the initial laser beam along a second optical path starting at one end thereof from the concave mirror; a Fabry-Perot element, disposed on the other end of the second optical path opposite to the one end thereof, and reflecting the initial laser beam back to the concave mirror so as to reflect the initial laser beam by the concave mirror along a third optical path starting at one end thereof from the concave mirror, wherein the Fabry-Perot element including a first surface and a second surface parallel to the first surface, wherein the first surface is closer to the concave mirror when compared to the second surface and has a first relatively high transmittance, and the second surface has a first relatively high reflectivity; and an output coupler disposed on the other end of the third optical path opposite to the one end thereof, and releasing the solid-state laser pulse having the pulse width; and (B) controlling the thickness to adjust the pulse width.

The mode-locked solid state laser apparatus and relevant methods provided by the present invention can be applied usefully in semiconductor manufacturing processes. Thus, the present invention has utility for industry.

The objectives and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed descriptions and accompanying drawings, in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for the purposes of illustration and description only; they are not intended to be exhaustive or to be limited to the precise form disclosed.

Please refer toFIG. 2, which shows one embodiment of the high power nanosecond mode-locked solid state laser apparatus100and the method thereof according to the present invention. As illustrated, the solid state laser device100includes an optical film11, an optical gain medium crystal12, a Fabry-Perot element110, a first mirror120, a second mirror130, a third mirror140and an output coupler15. The optical film11is disposed on a surface121of the optical gain medium crystal12facing the X direction, and receives the pumping light Lpumpincident in the X direction. According to an embodiment, the pumping light Lpumpis derived from a diode laser (not shown) having a wavelength of about 808 nm. The optical film11has high transmittance to incident lights having a wavelength of about 808 nm, and allows the pumping light Lpumpto enter the inside of the optical gain medium crystal12.

The optical gain medium crystal12comprises a neodymium doped vanadate (for example, Nd:YVO4), which can absorb the energy of the pumping light Lpumpvia the dopant to release an initial laser beam Liniwith a wavelength of about 1064 nm. As shown inFIG. 2, the initial laser beam Liniis projected in the direction along the first light path101starting from the surface121of the optical gain medium crystal12near the optical film11.

The Fabry-Perot element110is disposed on the other end of the first optical path101opposite to the one end, and reflects the initial laser beam Linialong a second optical path102having one end thereof starting from the Fabry-Perot element110. The present invention uses a reflected Fabry-Perot element110having a first surface111and a second surface113that are parallel to each other. The first surface111has high transmittance or low reflectivity (e.g., reflectivity less than 0.5% or even less than 0.2%) for lights with a wavelength of about 1064 nm, allowing most of the initial laser beam Linito penetrate, while the second surface113has high reflectivity (e.g., having a reflectivity greater than 99.8%). The distance between the first surface111and the second surface113is the thickness t of the Fabry-Perot element110. In the relative position, the first surface111is closer to the first mirror120when compared to the second surface113, and is also closer to the light source of the incident initial laser beam Liniwhich is the optical gain medium crystal12when compared to the second surface113, such that the initial laser beam Liniis repeatedly passed through the first surface111and reflected by the second surface113to generate an effect of Fabry-Perot interference.

The first mirror120is disposed on the other end of the second optical path102opposite to the one end of the second optical path102, and reflects the initial laser beam Linialong a third optical path103having one end thereof starting from the first mirror120. The second mirror130is disposed on the other end of the third optical path103opposite to the one end of the third optical path103, and reflects the initial laser beam Linialong a fourth optical path104having one end thereof starting from the second mirror130. The third mirror140is disposed on the other end of the fourth optical path104opposite to the one end of the fourth optical path104, and reflects the initial laser beam Linialong a fifth optical path105having one end thereof starting from the third mirror140. Basically, the combination of the first mirror120, the second mirror130and the third mirror140can be adjusted according to the need so as to achieve a required total length of optical path.

The output coupler15is disposed on the other end of the fifth optical path105opposite to the one end of the fifth optical path105, and may be formed of a multilayer thin film stack151(for example, 10 layers of aluminum arsenide or gallium arsenide film) disposed on the surface of a transparent semiconductor substrate153(for example, a gallium arsenide substrate). When the initial laser beam Liniis under a lower power condition, the multilayer thin film stack151of the output coupler15has high reflectivity (for example, a reflectivity of about 96.3%), and the initial laser beam Liniis reflected back along the fifth light path105in the reverse direction to the third mirror140.

Due to the reversibility of the optical path, those skilled in the art will appreciate that the initial laser beam Linimay return to the first optical path101from the fifth optical path105in the opposite direction and eventually arrive at the surface121of the optical gain medium crystal12with the optical film11disposed thereon. The optical film11has high reflectivity (for example, a reflectivity of at least 99.8% or higher) in a direction facing the optical gain medium crystal12, that is, in a direction facing the first optical path101for an incident light having a wavelength of about 1064 nm. The initial laser beam Linican return in the opposite direction along the first optical path101all the way to the other end of the fifth optical path105, that is, the location of the output coupler15.

The configuration described in the preceding paragraph forms a resonant cavity for the initial laser beam Lini. When the sum of the path lengths of the first to fifth optical paths101-105is a multiple of a half wavelength ½ λ, of the initial laser beam Lini, the initial laser beam Liniwill form a standing wave and continue to reciprocate between the optical film11and the output coupler15, and the power of the initial laser beam Liniwill be increased as the pumping light Lpumpbeing continuously transmitted into the optical gain crystal12. For example, when the total light path length is 1 meter, a light beam having wavelengths of about 1064 nm can form a standing wave with at least, for example, 1063.9950 nm, 1063.9956 nm, 1063.9962 nm, 1063.9968 nm, 1063.9973 nm, 1063.9978 nm, 1063.9984 nm, 1063.9990 nm, 1063.9996 nm, 1064.0002 nm, 1064.0007 nm, 1064.0012 nm, 1064.0018 nm, 1064.0024 nm, 1064.0030 nm, 1064.0035 nm, 1064.0041 nm, 1064.0046 nm, 1064.0052 nm and so on, wherein each of which can represent a resonant mode. In practice, taking the resonant cavity10shown inFIG. 1for example, the range for wavelengths representing resonant modes can be 0.5 nm or more without using any Fabry-Perot element. Therefore, the total number of modes is thousands to tens of thousands, and there can exist higher numbers of mode count with denser distribution of corresponding wavelengths for the total light path length which is longer. However, the number of modes existing in the laser cavity will be greatly reduced, and the wavelength distribution will be more concentrated, after a mode selection by means of the Fabry-Perot element.

Referring again toFIG. 2, as the pumping light Lpumpis continuously injected into the optical gain medium crystal12to increase the power of the initial laser beam Lini, the multilayer thin film stack151of the output coupler15will exhibit a high transmittance (e.g., a reflectivity of less than 5% or even less than 2%) and thereby transmits a laser pulse Lexitout of the solid state laser apparatus100when the intensity of the initial laser beam Linireaches a threshold. After the high-power laser light or pulse is released, the intensity of the initial laser beam Liniis lowered to an extremely low condition so that the multilayer thin film stack151of the output mirror15returns to a high reflectivity state, and the power of the initial laser beam Liniin the solid state laser apparatus100is again increased as the pumping light Lpumpcontinues to be injected into the optical gain medium crystal12. As a result, an intermittent solid-state laser pulse is continuously generated, and can provide various industrial applications.

Please refer toFIG. 3, which shows a high power nanosecond mode-locked solid state laser apparatus200and the method thereof of, according to a second embodiment of the present invention. According toFIG. 3, the solid state laser device200includes an optical film11, an optical gain medium crystal12, a Fabry-Perot element110, a first mirror220, a second mirror230, a third mirror240, and an output coupler15. The same as the preceding embodiment, the optical film11is disposed on a surface121of the optical gain medium crystal12facing the X direction, and receives the pumping light Lpumpincident in the X direction. The optical film11has high transmittance to incident lights, and allows the pumping light Lpumpto enter the inside of the optical gain medium crystal12. Detailed embodiments for the optical gain medium crystal12, the Fabry-Perot element110, the first mirror220, the second mirror230, the third mirror240and the output coupler15are the same as the ones set forth above, and thus there is no need to repeat.

The initial laser beam Liniis projected in the direction along the first light path201starting from the surface121of the optical gain medium crystal12near the optical film11. The Fabry-Perot element110is disposed on the other end of the first optical path201opposite to the one end, and reflects the initial laser beam Linialong a second optical path202having one end thereof starting from the Fabry-Perot element110. The first mirror220is disposed on the other end of the second optical path202opposite to the one end of the second optical path202, and reflects the initial laser beam Linialong a third optical path203having one end thereof starting from the first mirror220. The second mirror230is disposed on the other end of the third optical path203opposite to the one end of the third optical path203, and reflects the initial laser beam Linialong a fourth optical path204having one end thereof starting from the second mirror230back to the first mirror220. The first mirror is disposed at the other end of the fourth optical path204opposite to the one end of the fourth optical path204, and reflects the initial laser beam Linialong a fifth optical path205having one end thereof starting from the first mirror220and the other end at the second mirror230. The second mirror230reflects the initial laser beam Linialong a sixth optical path206having one end thereof starting from the second mirror230. The third mirror240is disposed on the other end of the sixth optical path206opposite to the one end of the sixth optical path206, and reflects the initial laser beam Linialong a seventh optical path207having one end thereof starting from the third mirror240.

The output coupler15is disposed on the other end of the seventh optical path207opposite to the one end of the seventh optical path207. When the initial laser beam Liniis under a lower power condition, the multilayer thin film stack151of the output coupler15has high reflectivity (for example, a reflectivity of about 96.3%), and the initial laser beam Liniis reflected back along the seventh light path207in the reverse direction to the third mirror240. On the other hand, when the intensity of the initial laser beam Linireaches a threshold, the multilayer thin film stack151of the output coupler15will exhibit a high transmittance (e.g., a reflectivity of less than 5% or even less than 2%) and thereby transmits a laser pulse Lexitout of the solid state laser apparatus200.

In the embodiment as shown inFIG. 3, the combination of the first mirror220, the second mirror230and the third mirror240can be adjusted according to the need so as to achieve a required total length of optical path. It is appreciated that, for the need of increasing the total length of the optical path in the cavity, the first and the second mirrors220,230are concave mirrors so a couple of additional optical paths204,205exist therebetween, compared with the embodiment shown inFIG. 2. As a result, the total number of available wavelengths about 1064 nm for forming standing waves can be increased. That is to say, the number of modes existing in the resonant cavity can be increased by such a manner. The skilled person in the art can choose appropriate combinations of mirrors to configure the needed optical paths, without going beyond the scope of the present invention.

In the embodiments shown inFIGS. 2 and 3, the Fabry-Perot element110is placed in the light path at the position where the initial laser beam Liniis first received. In a different embodiment, the Fabry-Perot element110can also be arranged at a relatively intermediate position in the light path. Please refer toFIG. 4, which shows a high power nanosecond mode-locked solid state laser apparatus300and the method thereof of, according to a third embodiment of the present invention. According toFIG. 4, the solid state laser device300includes an optical film11, an optical gain medium crystal12, a concave mirror320, a Fabry-Perot element110and an output coupler15. The same as the preceding embodiments, technical features of the optical film11, the optical gain medium crystal12, the Fabry-Perot element110and the output coupler15are the same as the ones set forth above, and thus there is no need to repeat.

The optical film11is disposed on a surface121of the optical gain medium crystal12facing the X direction, and receives the pumping light Lpumpincident in the X direction. The optical film11has high transmittance to incident lights, and allows the pumping light Lpumpto enter the inside of the optical gain medium crystal12for generating an initial laser beam Lini. The initial laser beam is projected along a first optical path301starting at one end thereof from the surface121of the optical gain medium crystal12near the optical film11. The concave mirror320is disposed on the other end of the first optical path301opposite to the one end of the first optical path301, and reflects the initial laser beam Linialong a second optical path302starting at one end thereof from the concave mirror320. The Fabry-Perot element110is disposed on the other end of the second optical path302opposite to the one end thereof, and reflects the initial laser beam Liniback to the concave mirror320along a third optical path303so as to have the initial laser beam Linireflected by the concave mirror320along a fourth optical path304starting at one end thereof from the concave mirror320.

The output coupler15is disposed on the other end of the fourth optical path304opposite to the one end of the fourth optical path304, and may be formed of a multilayer thin film stack151(for example, 10 layers of aluminum arsenide or gallium arsenide film) disposed on the surface of a transparent semiconductor substrate153(for example, a gallium arsenide substrate). When the initial laser beam Liniis under a lower power condition, the multilayer thin film stack151of the output coupler15has high reflectivity (for example, a reflectivity of about 96.3%), and the initial laser beam Liniis reflected back along the fourth light path304in the reverse direction to the concave mirror320. On the other hand, when the intensity of the initial laser beam Linireaches a threshold, the multilayer thin film stack151of the output coupler15will exhibit a high transmittance (e.g., a reflectivity of less than 5% or even less than 2%) and thereby transmits a laser pulse Lexitout of the solid state laser apparatus300.

The Fabry-Perot element110has a first surface111and a second surface113that are parallel to each other. The first surface111has high transmittance or low reflectivity (e.g., reflectivity less than 0.5% or even less than 0.2%) for lights with a wavelength of about 1064 nm, allowing most of the initial laser beam Linito penetrate, while the second surface113has high reflectivity (e.g., having a reflectivity greater than 99.8%). The distance between the first surface111and the second surface113is the thickness t of the Fabry-Perot element110. In the relative position, the first surface111is closer to the concave mirror320when compared to the second surface113, such that the initial laser beam Liniis repeatedly passed through the first surface111and reflected by the second surface113to generate an effect of Fabry-Perot interference. In the embodiments shown inFIGS. 2-4, the present invention replaces one of the mirrors in the laser resonate cavity with a reflected Fabry-Perot element for generating the Fabry-Perot interference in the optical path of the laser beam, which can effectively achieve the efficacy of mode selection.

Please refer toFIG. 5, which shows a comparison between the powers of the mode-locked solid state laser according to the present invention and that of the traditional mode-locked solid state laser. It can be seen fromFIG. 5that, the present invention can achieve a laser pulse of almost the same output power as a conventional solid-state laser resonant cavity with the same power pumping light input by using the reflected Fabry-Perot element. However, the method of using the traditional transmitted Fabry-Perot element ends up with lower power output as predicted, due to the additional optical elements in the optical path.

Please refer toFIG. 6, which shows a comparison between the mode types of the mode-locked solid state laser according to the present invention and that of the traditional mode-locked solid state laser. According to the illustration inFIG. 6, a solid-state laser device that does not use any mode-locking tool (such as the device shown inFIG. 1) has a modal distribution width of the output pulse that is relatively wide (a range of about 0.6 nm); using a conventional transmitted Fabry-Perot element (for example, a transmitted Fabry-Perot element16is added into the device configuration as shown inFIG. 1) can obtain a narrower distribution of the modal distribution of the output pulse (roughly 0.1 nm); and the solid-state laser device (for example, the device configuration shown inFIG. 4) using a reflected Fabry-Perot element can obtain excellent mode selection efficiency, and the output pulse has the narrowest modal distribution width (less than 0.003 nm, which is hard to identified in the illustration ofFIG. 6).

Please refer toFIG. 7, which shows a comparison between the mode selection effects of the mode-locked solid state laser according to the present invention and that of a mode-locked solid state laser equipped with a traditional Fabry-Perot element. Those skilled in the art can understand that the mode and bandwidth of the laser pulses are related parameters of different perspectives, so we can choose to observe the bandwidth of the laser pulse light to know the effect of the mode selection. Comparing the thickness of the Fabry-Perot element (the distance between the two parallel surfaces) and the bandwidth of the generated laser pulses, one can find a significant linear relationship between the thickness and the bandwidth of the laser pulse. Therefore, according to an embodiment of the invention, the control of width t can be used to control the bandwidth of the output laser pulse Lexit. On the contrary, the bandwidth of the output laser pulse is not significantly affected by the thickness when using the transmitted Fabry-Perot element, so the purpose of bandwidth adjustment cannot be achieved by means of controlling component thickness. It will be apparent that the method and apparatus of the present invention can fully and effectively achieve the efficacy of mode selection.

Through the abovementioned embodiments, the Raman laser for generating high-power and multiple-wavelength laser lights with visible wavelengths according to the present invention may use the linear resonance cavity under the same configuration, and can obtain high-power visible laser lights with different wavelengths by means of different device arrangement, which is a technology breakthrough.