Stabilized broadband light source apparatus and methods
A broadband light source apparatus, and corresponding method, includes a broadband light source configured to provide source light with a source wavelength spectrum having a centroid thermal sensitivity. The apparatus also includes a broadband optical filter characterized by a filter spectrum that has one or more spectral characteristics and a thermal sensitivity with magnitude and sign. The filter is configured to receive the source light and to deliver broadband output light with an output spectrum that is a function of the source and filter spectra and has an output centroid wavelength. The spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter are configured to minimize a thermal sensitivity of the output centroid wavelength. The filter can be configured in view of a particular source spectrum to stabilize output centroid wavelength and maximize total output power passively with respect to ambient temperature fluctuations.
1. A broadband light source apparatus comprising:
a broadband light source configured to provide broadband source light characterized by a source wavelength spectrum having a source centroid wavelength with a thermal sensitivity; and
a broadband optical filter characterized by a filter wavelength spectrum, the filter wavelength spectrum having one or more spectral characteristics, the filter wavelength spectrum further having a thermal sensitivity with magnitude and sign, the broadband optical filter configured to receive the source light and to deliver broadband output light characterized by an output wavelength spectrum that is a function of the source and filter wavelength spectra,
the broadband output light having an output centroid wavelength, the sign of the thermal sensitivity of the filter wavelength spectrum being opposite a sign of the thermal sensitivity of the source centroid wavelength, and the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum configured to minimize a thermal sensitivity of the output centroid wavelength,
wherein the broadband optical filter is an interference filter, and wherein the broadband light source and the interference filter are mechanically attached to a bi-material strip, and wherein the sign of the thermal sensitivity of the filter wavelength spectrum is an effective negative sign of the thermal sensitivity of the filter wavelength spectrum due to relative angular displacement of the broadband light source and the broadband optical filter as a function of ambient temperature.
2. The apparatus of claim 1 , wherein the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum are further configured to minimize the thermal sensitivity of the output centroid wavelength to within ±5 ppm/° C.
3. The apparatus of claim 2 , wherein the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum are further configured to minimize the thermal sensitivity of the output centroid wavelength to within ±0.5 ppm/° C.
4. The apparatus of claim 3 , wherein the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum are further configured to minimize the thermal sensitivity of the output centroid wavelength to within ±0.2 ppm/° C.
5. The apparatus of claim 1 , wherein the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum are further configured to minimize the thermal sensitivity of the output centroid wavelength over a temperature range of 10° C.
6. The apparatus of claim 1 , wherein the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum are configured such that a relative integrated output power of the broadband output light is maximized.
7. A fiber-optic gyroscope (FOG) including the broadband light source apparatus claim 1 , the FOG further including a coil of optical fiber and an optical coupling configured to couple the broadband output light into the coil of optical fiber.
8. A method for optimizing broadband light, the method comprising:
providing broadband source light characterized by a source wavelength spectrum having a source centroid wavelength thermal sensitivity;
configuring a broadband optical filter to be characterized by a filter wavelength spectrum, the filter wavelength spectrum having one or more spectral characteristics, the filter wavelength spectrum further having a thermal sensitivity with magnitude and sign, to receive the source light, and to deliver broadband output light characterized by an output wavelength spectrum that is a function of the source and filter wavelength spectra, the broadband output light having an output centroid wavelength, the sign of the thermal sensitivity of the filter wavelength spectrum being opposite a sign of the thermal sensitivity of the source centroid wavelength; and
configuring the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize a thermal sensitivity of the output centroid wavelength,
wherein configuring the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum includes using an interference filter mechanically attached to a bi-material strip to which a broadband light source providing the source light is also attached, and wherein configuring the sign of the thermal sensitivity of the filter wavelength spectrum also includes configuring an effective negative sign of the thermal sensitivity of the filter wavelength spectrum due to relative angular displacement of the light source and the broadband optical filter as a function of ambient temperature.
9. The method of claim 8 , wherein configuring the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize a thermal sensitivity of the output centroid wavelength includes configuring the spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize the thermal sensitivity of the output centroid wavelength to within ±5 ppm/° C.
10. The method of claim 9 , wherein configuring the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize a thermal sensitivity of the output centroid wavelength includes configuring the spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize the thermal sensitivity of the output centroid wavelength to within ±0.5 ppm/° C.
11. The method of claim 10 , wherein configuring the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize a thermal sensitivity of the output centroid wavelength includes configuring the spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize the thermal sensitivity of the output centroid wavelength to within ±0.2 ppm/° C.
12. The method of claim 8 , wherein configuring the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize a thermal sensitivity of the output centroid wavelength includes configuring the spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to minimize the thermal sensitivity of the output centroid wavelength over a temperature range of 10° C.
13. The method of claim 8 , further including configuring the one or more spectral characteristics and the magnitude and sign of the thermal sensitivity of the filter wavelength spectrum to maximize a relative integrated output power of the broadband output light.