Wavelength stabilization for broadband light sources
A broadband light source, such as a light-emitting diode (LED), such as a superluminescent light-emitting diode (SLED), has its mean wavelength stabilized by using a filter to pass a characteristic of the output of the source, detecting the filtered output, and adjusting a parameter affecting the wavelength of the source, such as drive current or temperature. A Gaussian or near-Gaussian filter can be used to obtain an intensity detection, or two narrowband filters can be used where one filter passes a wavelength greater, and one passes a wavelength less, than the desired mean wavelength.
1. An apparatus comprising:
a broadband light source for emitting light with a source mean wavelength;
a filter with a generally Gaussian spectral distribution for receiving light from the source for filtering the light to provide filtered light, the filter having a filter mean wavelength, the filter for filtering substantially all the light from the light source when the filter mean wavelength is substantially equal to the source mean wavelength;
a first detector for detecting the filtered light and for providing a signal indicative of a parameter of the filtered light; and
a control system responsive to the signal from the detector for controlling the mean wavelength of the light emitted from the source if the mean wavelength deviates from a desired value.
2. The apparatus of claim 1 , wherein the filter is spaced from the detector and housed in a separate component.
3. The apparatus of claim 1 , wherein the filter is formed on a surface of the detector.
4. The apparatus of claim 1 , wherein the source includes a light emitting diode (LED).
5. The apparatus of claim 1 , wherein the source includes a superluminescent light emitting diode (SLED).
6. The apparatus of claim 1 , wherein the source is mounted to a thermo-electric cooler (TEC), the control system controlling the mean wavelength by controlling the temperature of the TEC.
7. The apparatus of claim 1 , wherein the control system controls the mean wavelength by controlling a drive current to the source.
8. The apparatus of claim 1 , further comprising a second detector, and a beam splitter between the source and the filter for providing a first beam to the first detector and a second beam to the second detector, the control system being responsive also to a signal from the second detector.
9. The apparatus of claim 1 , further comprising an optical fiber for receiving light from the source.
10. The apparatus of claim 9 , further comprising a generally Gaussian filter between the source and the optical fiber.
11. The apparatus of claim 1 , further comprising a fiber optic gyroscope for receiving light from the source.
12. The apparatus of claim 11 , wherein the source includes a light emitting diode (LED).
13. The apparatus of claim 11 , wherein the source includes a superluminescent light emitting diode (SLED).
14. An apparatus comprising:
a broadband light source for emitting light with a mean wavelength;
a first narrowband filter for receiving light from the source and for passing light with a wavelength greater than the mean wavelength;
a second filter receiving light from the source and for passing light with a wavelength less than the mean wavelength;
a first detector for detecting light from the first filter and for providing a first signal;
a second detector for detecting light from the second filter and for providing a second signal; and
a control system responsive to the first and second signals and for controlling the mean wavelength of the light emitted from the source if the mean wavelength deviates from a desired value.
15. The apparatus of claim 14 , wherein the source includes a light emitting diode (LED).
16. The apparatus of claim 14 , wherein the source includes a superluminescent light emitting diode (SLED).
17. The apparatus of claim 14 , further comprising a beam splitter for receiving a beam from the source and providing first and second beams to the first and second filters.
18. The apparatus of claim 14 , wherein the source is mounted to a thermo-electric cooler (TEC), the control system controlling the mean wavelength by controlling the temperature of the TEC.
19. The apparatus of claim 14 , wherein the control system controls the mean wavelength by controlling a drive current to the source.
20. The apparatus of claim 14 , wherein each filter passes light with a wavelength where the intensity of the light from the source is about ⅔ of the peak intensity.
21. The apparatus of claim 14 , further comprising a fiber optic gyroscope for receiving light from the source.
22. The apparatus of claim 21 , wherein the source includes a light emitting diode (LED).
23. The apparatus of claim 21 , wherein the source includes a superluminescent light emitting diode (SLED).