Optical feedback stabilization of photonic microwave generation using period-one nonlinear dynamics of semiconductor lasers.

Kai-Hung Lo,Silvano Donati,Sheng-Kwang Hwang

doi:10.1364/oe.22.018648

Abstract

Effects of optical feedback on period-one nonlinear dynamics of an optically injected semiconductor laser are numerically investigated. The optical feedback can suppress the period-one dynamics and excite other more complex dynamics if the feedback level is high except for extremely short feedback delay times. Within the range of the period-one dynamics, however, the optical feedback can stabilize the period-one dynamics in such a manner that significant reduction of microwave linewidth and phase noise is achieved, up to more than two orders of magnitude. A high feedback level and/or a long feedback delay time are generally preferred for such microwave stabilization. However, considerably enhanced microwave linewidth and phase noise happen periodically at certain feedback delay times, which is strongly related to the behavior of locking between the period-one microwave oscillation and the feedback loop modes. The extent of these enhancements reduces if the feedback level is high. While the microwave frequency only slightly changes with the feedback level, it red-shifts with the feedback delay time before an abrupt blue-shift occurs periodically. With the presence of the laser intrinsic noise, frequency jitters occur around the feedback delay times leading to the abrupt blue-shifts, ranging from the order of 0.1 GHz to the order of 1 GHz.

Highlights

By introducing continuous-wave optical injection, period-one (P1) nonlinear dynamics can be excited through undamping the relaxation resonance of semiconductor lasers [1, 2]
While a regeneration of the optical injection appears at the offset frequency of 40 GHz because of the injection pulling effect [29], oscillation sidebands separated from the regeneration by an oscillation frequency f0 = 46.06 GHz emerge through undamping the laser relaxation resonance
Except the broadening around each spectral component and the appearance of the noise pedestal, these key features of the P1 dynamical state are observed when the laser noise is considered

Summary

Introduction

By introducing continuous-wave optical injection, period-one (P1) nonlinear dynamics can be excited through undamping the relaxation resonance of semiconductor lasers [1, 2]. Owing to the red-shifted cavity resonance enhancement [5,6,7], the lower oscillation sideband is typically much stronger than the upper one These unique characteristics of the P1 dynamics have attracted increasing research interest for a variety of different optical and microwave signal processing applications. While a similar reduced linewidth can be achieved for microwaves up to 23 GHz, a photodetector, an electronic microwave amplifier, and an electronic microwave attenuator, which operate at the same microwave frequency, are required in the optoelectronic feedback loop Since both approaches need electronic microwave components, they become increasingly difficult or/and expensive to implement for increasingly high-frequency microwave applications. The linewidth can be reduced below 50 kHz for microwaves up to 45 GHz. Apparently, the optical feedback approach is much preferred and attractive for high-frequency microwave applications because of its all-optical nature, which bypasses the bandwidth restriction of electronics.

Numerical model

Dynamical characteristics

Microwave characteristics

Conclusion