Amplitude noise reduction in semiconductor lasers with weak, dispersive optical feedback

Area of Science:

• Optics
• Semiconductor Physics
• Quantum Optics

Background:

• Semiconductor lasers are crucial light sources but suffer from intrinsic amplitude noise.
• Optical feedback can modify laser noise characteristics, with potential for noise reduction.
• Dispersive loss in an external cavity is explored as a method to control feedback effects.

Purpose of the Study:

• To theoretically and experimentally investigate the effect of weak optical feedback with dispersive loss on semiconductor laser amplitude noise.
• To quantify the noise reduction achieved and compare it with theoretical predictions.
• To assess the feasibility of this technique for generating amplitude-squeezed light.

Main Methods:

• Development of a theoretical model for amplitude noise spectrum under weak optical feedback with dispersive loss.
• Experimental setup involving a semiconductor laser coupled to an external cavity with a dispersive element.
• Measurement of the laser's amplitude noise spectrum at various injection currents and feedback levels.

Main Results:

• A significant reduction in the low-frequency amplitude noise spectrum was observed, up to 7 dB.
• Theoretical predictions for noise reduction were closely matched by experimental measurements.
• An increase in noise was noted at frequencies related to the external cavity's free spectral range.

Conclusions:

• Weak optical feedback combined with dispersive loss effectively reduces amplitude noise in semiconductor lasers.
• The observed noise reduction validates the theoretical model and demonstrates a practical method for noise suppression.
• This technique holds promise for the generation of high-quality amplitude-squeezed light for various applications.