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Speckle-displacement-based wavemeter for mode-hop and side-mode detection.
Applied Optics
|February 24, 2022
Summary
This study introduces a novel speckle-displacement wavemeter for distributed Bragg reflector (DBR) tapered lasers. This device accurately measures wavelength shifts, mode hops, and side-mode suppression ratios (SMSRs) for stable laser output.
Area of Science:
- Optics and Photonics
- Laser Physics
- Metrology
Background:
- Distributed Bragg reflector (DBR) tapered lasers can suffer from multimode operation, affecting output directionality.
- Accurate characterization of laser wavelength, mode hops, and side-mode suppression ratio (SMSR) is crucial for various applications.
Purpose of the Study:
- To develop and validate a speckle-displacement-based wavemeter combined with a spatial filter.
- To eliminate the influence of multimode operation on laser output directionality.
- To demonstrate the measurement of mode hops and SMSRs.
Main Methods:
- A speckle-displacement wavemeter was integrated with a spatial-fundamental-mode-pass filter.
- The setup utilizes laser illumination of a rough surface and observation of back-scattered speckle patterns.
- Speckle pattern shifts, tracked via covariance function peaks, correlate with wavelength changes.
Main Results:
- The wavemeter achieved a spectral resolution of 10.4 MHz.
- Mode hops did not cause significant speckle pattern decorrelation.
- The side-mode suppression ratio (SMSR) was found to correlate with the covariance function's peak height and width.
Conclusions:
- The developed wavemeter effectively measures wavelength, mode hops, and SMSRs.
- This technique is valuable for applications requiring stable single-frequency laser light, such as spectroscopy and quantum optics.
- The system offers a robust method for characterizing diode lasers.
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