Modulation Characteristics of Period-One Oscillations in Quantum Cascade Lasers

Binbin Zhao,Yibo Peng,Xingguang Wang,Cheng Wang

doi:10.3390/app112411730

Abstract

Quantum cascade lasers subject to tilted optical feedback produce periodic oscillations, quasi-periodic oscillations, and low-frequency oscillations. This work presents the modulation characteristics of period-one (P1) oscillations in a quantum cascade laser with tilted optical feedback. The electrical signal at the oscillation frequency is more than 50 dB higher than the noise level, and the electrical linewidth is less than 2.0 kHz. This electrical linewidth is about four orders of magnitude narrower than the optical linewidth (around 16 MHz) of the free-running laser, which suggests that the optical sidebands induced by the P1 oscillations are highly coherent with the main optical mode. In addition, the modulation depth of the optical signal is found to be in the range of 1% to 3.5%. In addition, it is verified in the simulations that the P1 oscillations induce not only amplitude modulation but also frequency modulation due to the phase-amplitude coupling effect.

Highlights

Semiconductor lasers subjected to external optical feedback usually produce rich nonlinear dynamics, including periodic oscillations, quasi-periodic oscillations, and chaotic oscillations [1]
In order to show the optical sidebands induced by the P1 oscillation, we simulate the optical spectrum using the rate equation approach, which takes into account the effect of tilted optical feedback [22,23,37]
We have unveiled the modulation characteristics of P1 oscillations in a quantum cascade lasers (QCLs) subject to optical feedback

Summary

Introduction

Semiconductor lasers subjected to external optical feedback usually produce rich nonlinear dynamics, including periodic oscillations, quasi-periodic oscillations, and chaotic oscillations [1] Among these dynamics, chaos is the most well-known and has been used for applications of secure communication [2,3], random bit generation [4,5], Lidar systems [6], and reservoir computing networks [7,8]. Our recent work found that QCLs can be more destabilized by using tilted optical feedback, where the reflection mirror is misaligned from the optical path [22] In this configuration, we have observed periodic oscillations, quasi-periodic oscillation, and low-frequency oscillations at different mirror-tilt angles [22,23]

Methods

Discussion

Conclusion