US-12625067-B2 - Spectrometer with rotated volume Bragg grating

Abstract

A spectrometer may include a rotated volume Bragg grating (r-VBG) within a volume of a material having an input face, where the r-VBG reflects portions of input light propagating through the input face that satisfies a Bragg condition for wavelengths within a spectral band, where a period of the r-VBG along the grating vector is chirped to vary along the grating vector to provide that the Bragg condition is satisfied for different wavelengths at different depths, and where a spectrum of the input light is spatially resolved in the reflected portions of the input light by the r-VBG. The spectrometer may further include a multi-pixel detector configured to receive the reflected portions of the input light from the r-VBG, where the multi-pixel detector is configured to output spectral data indicative of the spectrum of the input light within the spectral band.

Inventors

• Ivan Divliansky
• Ayman Abouraddy
• Leonid Glebov
• Oussama MHIBIK
• Murat Yessenov

Assignees

• UNIVERSITY OF CENTRAL FLORIDA RESEARCH FOUNDATION, INC.

Dates

Publication Date

20260512

Application Date

20231207

Claims (20)

1. 1 . A spectrometer comprising: a rotated volume Bragg grating (r-VBG) within a volume of a material having an input face, wherein the r-VBG is formed as planes of refractive index variation with periodicity along a grating vector at a non-zero angle relative to a normal vector of the input face, wherein the r-VBG reflects portions of input light propagating through the input face that satisfies a Bragg condition for wavelengths within a spectral band, wherein a period of the r-VBG along the grating vector is chirped to vary along the grating vector to provide that the Bragg condition is satisfied for different wavelengths at different depths, wherein a spectrum of the input light is spatially resolved in the reflected portions of the input light by the r-VBG; and a multi-pixel detector configured to receive the reflected portions of the input light from the r-VBG, wherein the multi-pixel detector is configured to output spectral data indicative of the spectrum of the input light within the spectral band.
2. 2 . The spectrometer of claim 1 , wherein the non-zero angle between the normal vector of the input face and the grating vector of the r-VBG is 45 degrees.
3. 3 . The spectrometer of claim 1 , further comprising: a controller including one or more processors configured to execute program instructions causing the one or more processors to: receive the data from the multi-pixel detector; and calibrate the spectral data based on calibration data to provide calibrated spectral data.
4. 4 . The spectrometer of claim 1 , further comprising: a display configured to provide a visual representation of the spectrum of the input light.
5. 5 . The spectrometer of claim 1 , wherein the multi-pixel detector is in contact with an output face of the material.
6. 6 . The spectrometer of claim 1 , wherein the period of the r-VBG along the grating vector is chirped to vary monotonically along the grating vector.
7. 7 . The spectrometer of claim 1 , wherein the period of the r-VBG along the grating vector is chirped to vary linearly along the grating vector.
8. 8 . The spectrometer of claim 1 , wherein the period of the r-VBG along the grating vector is chirped with a distribution selected to provide that the reflected portions of the input light by the r-VBG are spatially resolved across the output face within a distribution that is linear as a function of wavelength.
9. 9 . The spectrometer of claim 1 , wherein the multi-pixel detector comprises: at least one of a charge coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS) device, or an array of photodiodes.
10. 10 . The spectrometer of claim 1 , further comprising: an additional r-VBG, wherein the additional r-VBG is formed as planes of refractive index variation with periodicity along one or more additional grating vectors at one or more additional non-zero angles relative to the normal vector of the input face, wherein the additional r-VBG reflects portions of input light propagating along the incidence vector through the input face that satisfies a Bragg condition for wavelengths within an additional spectral band, wherein a period of the additional r-VBG along the additional grating vector is chirped to vary along the grating vector to provide that the Bragg condition is satisfied for different wavelengths within the additional spectral band at different depths, wherein the spectrum of the input light in the additional spectral band is spatially resolved in the reflected portions of the input light by the additional r-VBG; and an additional multi-pixel detector configured to receive the reflected portions of the input light from the additional r-VBG through the additional output face, wherein the multi-pixel detector is configured to output additional spectral data indicative of a spectrum of the input light in the additional spectral band.
11. 11 . The spectrometer of claim 10 , wherein the non-zero angle between the normal vector of the input face and the grating vector of the r-VBG is +45 degrees, wherein the non-zero angle between the normal vector of the input face and the grating vector of the additional r-VBG is −45 degrees.
12. 12 . The spectrometer of claim 10 , wherein the spectral band and the additional spectral band are non-overlapping.
13. 13 . The spectrometer of claim 10 , wherein the spectral band and the additional spectral band at least partially overlap.
14. 14 . A method comprising: directing input light through an input face of a material including a rotated chirped volume Bragg grating (r-VBG) within a volume of the material, wherein the r-VBG is formed as planes of refractive index variation with periodicity along a grating vector at a non-zero angle relative to a normal vector of the input face, wherein the r-VBG reflects portions of input light propagating along an incidence vector through the input face that satisfies a Bragg condition for wavelengths within a spectral band, wherein a period of the r-VBG along the grating vector is chirped to vary along the grating vector to provide that the Bragg condition is satisfied for different depths, wherein the reflected portions of the input light by the r-VBG are spatially resolved in the reflected portions of the input light by the r-VBG; and capturing the reflected portions of the input light from the output face with a multi-pixel detector; determining a spectrum of the input light within the spectral band based on output spectral data from the multi-pixel detector.
15. 15 . The method of claim 14 , wherein the non-zero angle between the normal vector of the input face and the grating vector of the r-VBG is 45 degrees.
16. 16 . The method of claim 14 , further comprising: calibrating the spectral data received from the multi-pixel detector.
17. 17 . The method of claim 14 , further comprising: displaying a visual representation of the spectrum of the input light on a display.
18. 18 . The method of claim 14 , wherein the multi-pixel detector is in contact with an output face.
19. 19 . The method of claim 14 , wherein the period of the r-VBG along the grating vector is chirped to vary monotonically along the grating vector.
20. 20 . The method of claim 14 , wherein the period of the r-VBG along the grating vector is chirped to vary linearly along the grating vector.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 63/430,805, filed Dec. 7, 2022, which is incorporated herein by reference in the entirety. TECHNICAL FIELD The present disclosure relates generally to spectrometers and, more particularly, to spectrometers incorporating rotated volume Bragg gratings. BACKGROUND It is often highly desirable to miniaturize optical components to provide compact and robust implementation. However, in many cases, miniaturization of optical components does not eliminate free-space propagation requirements and thus provides only limited impact. For example, replacing a conventional lens with an ultrathin metasurface may reduce the physical size of the lens, but does not substantially reduce the free-space propagation length required for image formation. As another example, traditional techniques for miniaturizing components within optical spectrometers suitable for spatially resolving the spectrum of light do not substantially impact free-space propagation requirements and thus also has limited impact on overall device size. There is therefore a need to develop systems and methods to address the above deficiencies. SUMMARY A spectrometer is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In embodiments, the spectrometer includes a rotated volume Bragg grating (r-VBG) within a volume of a material having an input face, wherein the r-VBG is formed as planes of refractive index variation with periodicity along a grating vector at a non-zero angle relative to a normal vector of the input face, wherein the r-VBG reflects portions of input light propagating through the input face that satisfies a Bragg condition for wavelengths within a spectral band, wherein a period of the r-VBG along the grating vector is chirped to vary along the grating vector to provide that the Bragg condition is satisfied for different wavelengths at different depths, wherein a spectrum of the input light is spatially resolved in the reflected portions of the input light by the r-VBG. In embodiments, the spectrometer includes a multi-pixel detector configured to receive the reflected portions of the input light from the r-VBG, wherein the multi-pixel detector is configured to output spectral data indicative of the spectrum of the input light within the spectral band. In embodiments, the non-zero angle between the normal vector of the input face and the grating vector of the r-VBG is 45 degrees. In embodiments, the spectrometer further includes a controller including one or more processors configured to execute program instructions causing the one or more processors to receive the data from the multi-pixel detector and calibrate the spectral data based on calibration data to provide calibrated spectral data. In embodiments, the spectrometer further includes a display configured to provide a visual representation of the spectrum of the input light. In embodiments, the multi-pixel detector is in contact with an output face of the material. In embodiments, the period of the r-VBG along the grating vector is chirped to vary monotonically along the grating vector. In embodiments, the period of the r-VBG along the grating vector is chirped to vary linearly along the grating vector. In embodiments, the period of the r-VBG along the grating vector is chirped with a distribution selected to provide that the reflected portions of the input light by the r-VBG are spatially resolved across the output face within a distribution that is linear as a function of wavelength. In embodiments, the multi-pixel detector includes at least one of a charge coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS) device, or an array of photodiodes. In embodiments, the spectrometer includes an additional r-VBG, wherein the additional r-VBG is formed as planes of refractive index variation with periodicity along one or more additional grating vectors at one or more additional non-zero angles relative to the normal vector of the input face, wherein the additional r-VBG reflects portions of input light propagating along the incidence vector through the input face that satisfies a Bragg condition for wavelengths within an additional spectral band, wherein a period of the additional r-VBG along the additional grating vector is chirped to vary along the grating vector to provide that the Bragg condition is satisfied for different wavelengths within the additional spectral band at different depths, and where the spectrum of the input light in the additional spectral band is spatially resolved in the reflected portions of the input light by the additional r-VBG. In embodiments, the spectrometer includes an additional multi-pixel detector configured to receive the reflected portions of the input light from the additional r-VBG through the additional output face, wherein the multi-pixel detector