Compact, Low Cost Raman Monitor For Single Substances
Apparatus for performing Raman spectroscopy may include a first laser source having a first emission wavelength and a second laser source having a second emission wavelength. A separation between the first and second emission wavelengths may correspond to a width of a Raman band of a substance of interest. A switch may provide switching between the first and second laser sources. An ensemble of laser emitters may be provided. A Bragg grating element may receive laser light from the ensemble. An optical system may direct light from the Bragg grating element into an optical fiber. A combined beam through the optical fiber may contain light from each of the emitters.
1 . Apparatus for performing Raman spectroscopy, the apparatus comprising:
an ensemble of laser emitters, the ensemble being adapted to emit first laser light having a first wavelength and second laser light having a second wavelength, wherein a separation between the first and second wavelengths corresponds to a width of a Raman band of a substance of interest;
a beam transformation system that receives the first laser light and the second laser light, and rotates images of the laser emitters by 90 degrees; and
an optical system that is adapted to form a combined beam that contains light at each of the first and second wavelengths.
2 . The apparatus of claim 1 , wherein each of the laser emitters is a p-n junction.
3 . The apparatus of claim 1 , wherein the laser emitters are respective p-n junctions in a single chip.
4 . The apparatus of claim 1 , wherein the laser emitters are individually addressable to emit respective laser light sequentially.
5 . The apparatus of claim 1 , further comprising a fast-axis collimator between the ensemble of laser emitters and the beam transformation system.
6 . The apparatus of claim 1 , further comprising a slow-axis collimator between the beam transformation system and the optical system.
7 . The apparatus of claim 1 , wherein the ensemble is further adapted to emit third laser light having a third wavelength, and wherein a separation between the second and third wavelengths corresponds to a width of a second Raman band of the substance of interest.
8 . The apparatus of claim 1 , wherein the ensemble is further adapted to emit third laser light having a third wavelength, and wherein a separation between the second and third wavelengths corresponds to a width of a Raman band of a second substance of interest.
9 . The apparatus of claim 1 , further comprising a Bragg grating element that is adapted to receive the first laser light and the second laser light, wherein the Bragg grating element reflects a respective portion of the light it receives from each of the emitters back into the emitters as a narrowband seed that causes each of the emitters to lase at its respective wavelength.
10 . The apparatus of claim 9 , wherein the Bragg grating element has a longitudinal axis, and has recorded therein a Bragg grating having a period that varies as a function of position along the longitudinal axis of the Bragg grating element.