Patent Publication Number: US-2019170579-A1

Title: Micro-scale waveguide spectroscope

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2017-0164335, filed on Dec. 1, 2017, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     Apparatuses consistent with exemplary embodiments relate to spectroscopes, and more particularly, to micro-scale waveguide spectroscopes. 
     2. Description of the Related Art 
     A spectroscope is an apparatus that disperses light such that the spectrum of the light may be observed and analyzed with the naked eye. A spectroscope may be used for determining the structure and composition of a material that emits and absorbs light. Spectroscopes include prism spectroscopes that use a prism, grating spectroscopes that use a diffraction grating, and interference spectroscopes that use light interference. 
     SUMMARY 
     One or more exemplary embodiments may provide micro-scale waveguide spectroscopes that have a simple configuration and are configured to increase portability. 
     According to an aspect of an exemplary embodiment, a micro-scale waveguide spectroscope includes: a waveguide having a bent region that does not satisfy a total internal reflection condition; and a light detector disposed such that light emitted from the waveguide through the bent region is incident thereon, and configured to detect light emitted from the bent region. 
     The waveguide may include a single layer having a refractive index greater than that of air. The waveguide may include a core layer and a cladding layer surrounding the core layer. 
     The waveguide may have a provided length and may have a spiral structure having a radius of curvature which gradually decreases from a first end of the waveguide to a second end of the waveguide. The waveguide may have a zigzag form, and bent regions of the zigzag form have gradually increasing radii of curvature. 
     The core layer may be an air layer, and the cladding layer may be a multi-reflection layer inwardly reflecting light incident thereon from the core layer. 
     The core layer may be a first material layer having a refractive index greater than air, and the cladding layer may be a second material layer having a refractive index less than that of the first material layer. 
     The light detectors may each include an optical device performing a photoelectric conversion operation. 
     The waveguide may have a plurality of bent regions, and radii of curvature of the bending regions may be different from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other exemplary aspects and advantages will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a plan view of a micro-scale waveguide spectroscope according to an exemplary embodiment; 
         FIGS. 2A, 2B, and 2C  are graphs of wavelength-intensity with respect to light detected by three light detectors of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along line  3 - 3 ′ of the waveguide of  FIG. 1 , which illustrates an exemplary configuration of the waveguide; 
         FIG. 4  is a cross-sectional view taken along line  3 - 3 ′ of the waveguide of  FIG. 1 , which illustrates another exemplary configuration of the waveguide; 
         FIG. 5  is a plan view of a micro-scale waveguide spectroscope according to another exemplary embodiment; 
         FIG. 6  shows a configuration of a micro-scale waveguide spectroscope according to another exemplary embodiment; and 
         FIG. 7  is a magnified view of a first region A 1  of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     Micro-scale waveguide spectroscopes according to exemplary embodiments will now be described in detail with reference to the accompanying drawings. In the drawings, thicknesses of layers or regions may be exaggerated for clarity of specification. 
       FIG. 1  shows a micro-scale waveguide spectroscope (hereinafter, a first waveguide spectroscope)  100  according to an exemplary embodiment. 
     Referring to  FIG. 1 , the first waveguide spectroscope  100  includes a waveguide  10  and a plurality of light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22 . The waveguide  10  is substantially in the shape of an elongated line having a certain length, and is formed into a spiral structure in which a diameter of the spiral is gradually reduced, proceeding from a first end of the waveguide  10  to a second end of the waveguide  10 . For convenience, six light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22  are depicted. However, the number of light detectors may be more than six or less than six according to a wavelength region or band of light to be detected. The light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22  may be arranged along the waveguide  10 . 
     Light L entering the waveguide  10  progresses along the waveguide  10  through internal total reflection. The waveguide  10  has a structure in which some portions of the waveguide  10  satisfy the total reflection condition but some other portions of the waveguide  10  do not satisfy the total reflection condition. That is, the waveguide  10  includes some sections that satisfy the total reflection condition and first through sixth regions P 1  through P 6  that do not satisfy the total reflection condition. The first through sixth regions P 1  through P 6  that do not satisfy the total reflection condition are arranged between the sections that satisfy the total reflection condition. The first through sixth regions P 1  through P 6  respectively correspond to the locations of the light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22 . In the first through sixth regions P 1  through P 6  that do not satisfy the total reflection condition in the waveguide  10 , lights L 1  through L 6  are discharged to the outside of the waveguide  10 . The spectra of the light L 1  through L 6  that is discharged to the outside of the waveguide  10 , respectively through the first through sixth regions P 1  through P 6 , may be different from each other. Curvatures of the first through sixth regions P 1  through P 6  may be different from each other. For example, the curvature of the waveguide at the regions P 1  through P 6  may increase from the first region P 1  through the sixth region P 6 . Also, the distance that the light travels within the waveguide  10 , prior to being emitted via one of the regions P 1  through P 6 , may be different from each other. Accordingly, a central wavelength and an intensity of the light emitted from each of the first through sixth regions P 1  through P 6  may be different. The curvatures of the first through sixth regions P 1  through P 6  may be controlled in the process of manufacturing the waveguide  10 . Accordingly, the curvatures of the regions P 1  though P 6  may be set in order to control a desired central wavelength of the light emitted from each of the regions P 1  through P 6 . In this way, by setting the curvatures of the first through sixth regions P 1  through P 6 , the central wavelengths of light emitted from the first through sixth regions P 1  through P 6  may be controlled to be different. 
     The number of the light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22  may be equal to the number of the regions P 1  through P 6  that do not satisfy the total reflection condition. Accordingly, the light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22  may each correspond to one of the regions P 1  through P 6 . There may be a one-to-one relationship between the regions P 1  through P 6  and the light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22 . The light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22  may each be a device that performs a photoelectric conversion operation. For example, the devices may be photo diodes. 
     Since the curvatures of the first through sixth regions P 1  through P 6  are set to be different in the process of manufacturing the waveguide  10 , light of a specific wavelength is emitted from each of the first through sixth regions P 1  through P 6  of the waveguide  10 . Accordingly, the components and intensity of a wavelength of the light L incident to the waveguide  10 , that is, the overall spectrum of the incident light L, may be obtained by detecting and analyzing the light emitted through the first through sixth regions P 1  through P 6 . 
     As discussed above, the curvatures of the first through sixth regions P 1  through P 6  are set in the process of manufacturing the waveguide  10  so that light of a specific wavelength is emitted from each of the first through sixth regions P 1  through P 6 . However, in addition to light of the specific wavelength, the light emitted through each of the first through sixth regions P 1  through P 6  of the waveguide  10  may also include some light of wavelengths adjacent to the specific wavelength. 
     For convenience of explanation, in the following description with respect to  FIGS. 2A through 2C , it is assumed that the waveguide  10  includes light leaking regions P 1 , P 3 , and P 5 , and that light detectors  12 ,  16 , and  20  are respectively at the first, third, and fifth regions P 1 , P 3 , and P 5 . 
       FIG. 2A  shows the wavelength-intensity of light measured by the first light detector  12  with respect to light emitted through the first region P 1 .  FIG. 2B  shows the wavelength-intensity of light measured by the third light detector  16  with respect to light emitted through the third region P 3 .  FIG. 2C  shows the wavelength-intensity of light measured by the fifth light detector  20  with respect to light emitted through the fifth region P 5 . 
     Referring to  FIG. 2A , light emitted through the first light leaking region P 1  includes light having a third wavelength λ 3  as a central wavelength, and in addition to the light having the third wavelength λ 3 , also includes light having first and second wavelengths λ 1  and λ 2  which have intensities less than that of the third wavelength λ 3 . 
     Referring to  FIG. 2B , light emitted through the third light leaking region P 3  includes light having a second wavelength λ 2 , as a central wavelength, together with light having first and third wavelengths λ 1  and λ 3 , which have intensities less than that of the second wavelength λ 2 . 
     Referring to  FIG. 2C , light emitted through the fifth light leaking region P 5  includes light having a first wavelength λ 1 , as a central wavelength, together with light having second and third wavelengths λ 2  and λ 3 , which have intensities less than that of the first wavelength λ 1 . 
     The overall spectrum of light L incident into the waveguide  10  may be obtained based on information regarding the light emitted through the first, third, and fifth regions P 1 , P 3 , and P 5 . 
     The light L incident into the waveguide  10  may include specific information. For example, the light L may be light emitted from a specific sample, or light that has passed through a specific part of an object and includes biological information with respect to the object. 
     Accordingly, when the overall spectrum of the light L is known, information with respect to the specific sample or biological information with respect to the object may be obtained from the light L. 
     The first waveguide spectroscope  100  described above and second and third waveguide spectroscopes  200  and  300  of  FIGS. 5 and 6  are micro-scale waveguide spectroscopes. For example, the first waveguide spectroscope  100  may have a size of approximately 100 μm or a few hundreds of μm, but is not limited thereto. 
     Since the first through third waveguide spectroscopes  100 ,  200 , and  300  are micro-scale waveguide spectroscopes, the first through third waveguide spectroscopes  100 ,  200 , and  300  may be miniaturized for use on a chip. Accordingly, the first through third waveguide spectroscopes  100 ,  200 , and  300  may be used as portable spectroscopes or spectrum analyzers, and thus, the approach to a sample is easy and an analyzing result may be readily and rapidly obtained. 
     The upper limit of the micro scale of the first waveguide spectroscope  100  may be determined as follows. When the size of the first waveguide spectroscope  100  is increased while the form thereof is maintained, the light leaking from one or more of the first through sixth regions P 1  through P 6  may stop at a certain point. Thus, this point may be regarded as the upper limit of an increase in the size of the first waveguide spectroscope  100 . This description may also be applied to the second and third first waveguide spectroscopes  200  and  300 . 
     The waveguide  10  may have a configuration including a single material layer having a refractive index greater than that of air. However, the configuration of the waveguide  10  is not limited thereto, and may be any of various types.  FIGS. 3 and 4  show various examples of configurations of the waveguide  10 . 
       FIG. 3  is a cross-sectional view taken along line  3 - 3 ′ of the waveguide  10  of  FIG. 1 . 
     Referring to  FIG. 3 , the waveguide  10  includes a core layer  10 A and a cladding layer  10 B that surrounds the core layer  10 A. The cladding layer  10 B has a refractive index less than that of the core layer  10 A. 
       FIG. 4  is a cross-sectional view taken along line  3 - 3 ′ of the waveguide  10  of  FIG. 1  as another example of the waveguide  10 . 
     Referring to  FIG. 4 , the waveguide  10  includes a core layer  32  and a multi-reflection layer  34  that surrounds the core layer  32 . The multi-reflection layer  34  may be a Distributed Bragg reflector (DBR) layer. The core layer  32  may be an air layer. The multi-reflection layer  34  may have a refractive index greater than that of air. For convenience, it is depicted that the multi-reflection layer  34  includes first through fourth material layers  34   a  through  34   d . However, the multi-reflection layer  34  may include more than or less than four material layers. In the multi-reflection layer  34 , the refractive index may be increased from the first material layer  34   a  towards the fourth material layer  34   d , but the present exemplary embodiment is not limited thereto. That is, so long as light progressing towards the multi-reflection layer  34  from the core layer  32  can be reflected toward the core layer  32 , the multi-reflection layer  34  may have any of various refractive index distributions. 
       FIG. 5  is a plan view of a micro-scale waveguide spectroscope (the second waveguide spectroscope)  200  according to another exemplary embodiment. 
     Referring to  FIG. 5 , the second waveguide spectroscope  200  includes a waveguide  40  and a plurality of light detectors  42 ,  44 ,  46 ,  48 ,  50 ,  52 ,  54 , and  56 . The number of the light detectors  42 ,  44 ,  46 ,  48 ,  50 ,  52 ,  54 , and  56  may be increased or reduced. The waveguide  40  may have a zigzag form. The waveguide  40  may have a wave form spreading in a direction. The radius of curvature of the wave may be gradually reduced towards a right side (i.e. from a first end of the waveguide  40  to a second end of the waveguide  40 ), and thus, the curvature of the waveguide  40  at each of the light detectors  42 ,  44 ,  46 ,  48 ,  50 ,  52 ,  54 , and  56  may differ. Portions of the waveguide  40  corresponding to the light detectors  42 ,  44 ,  46 ,  48 ,  50 ,  52 ,  54 , and  56  are regions that do not satisfy the total reflection condition, that is, regions from which light leaks to the outside of the waveguide  40 . A cross-section of the waveguide  40  may be the same as one of the cross-sections shown in  FIGS. 3 and 4 . The light detectors  42 ,  44 ,  46 ,  48 ,  50 ,  52 ,  54 , and  56  may each be a device performing a photoelectric conversion operation. For example, the devices may be photodiodes. 
       FIG. 6  is a plan view of a micro-scale waveguide spectroscope (the third waveguide spectroscope)  300  according to another exemplary embodiment. The third waveguide spectroscope  300  is a modified version of the second waveguide spectroscope  200  of  FIG. 5 . 
     Referring to  FIG. 6 , the third waveguide spectroscope  300  includes a waveguide  60  having a zigzag form progressing in a right direction and a plurality of light detectors  62  each arranged at bending regions of the waveguide  60 . Portions of the waveguide  60  between the light detectors  62  of the waveguide  60  may be straight lines. A configuration of the waveguide  60  may be the same as that of the waveguide  10  of the first waveguide spectroscope  100  of  FIG. 1 . The light detectors  62  may also be the same as the light detectors  12 ,  14 ,  16 ,  18 ,  20 , and  22  of the first waveguide spectroscope  100 . 
       FIG. 7  shows a magnified view of the first region A 1  of  FIG. 6 . 
     Referring to  FIG. 7 , the bending portion of the waveguide  60  has a curvature breaking a total reflection condition. Accordingly, total internal reflection does not occur at the bending portion. The light detector  62  is positioned to correspond to the bending portion of the waveguide  60 . 
     With reference to  FIG. 7 , the bending regions of the waveguide  60  of the third waveguide spectroscope  300  of  FIG. 6  have different curvatures, and thus, it may be seen that central wavelengths of lights emitted from the bending regions are also different from each other. 
     While one or more exemplary embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.