Injection locking of VCSELs

Abstract

Injection locking has been actively researched for its possibility to improve laser performance for both digital and analog applications. When a modulated follower laser (also termed "slave" laser) is locked to the master laser, its nonlinear distortion and frequency chirp may be reduced. As well, the resonance frequency can increase to several times higher than its free running case. In this paper, we show that the frequency response (S21) of an injection-locked laser is similar to a parasitic-limited laser with a high resonance frequency. The S21 was studied experimentally and the condition to achieve a flat, enhanced frequency response was identified. For analog applications, a record 112 dB-Hz 2 3 , single-tone third harmonic spur-free dynamic range of a 1.55m vertical cavity surface emitting lasers (VCSEL) was demonstrated. An improvement was attained for a wide-injection parameter space. In a 50-km 2.5-Gb/s digital link, a 2-dB power penalty reduction at 10 9 bit error rate was also demonstrated. As a novel application, an injection-locked uncooled tunable VCSEL was shown to have a reasonable modulation performance in a wide abient temperature range. The VCSEL was locked to a designated wavelength and the injection compensated the temperature-induced performance degradation. This concept can be extremely attractive for low-cost dense wavelength division muliplexed transmitters.

Slow light in semiconductor heterostructures

“…Typically, the injection locking configuration uses one continuous-wave (CW) operated laser as the master laser to optically lock a second directlymodulated slave laser. This technique has been shown to be very effective to improve various modulation characteristics of the slave laser, including a reduced frequency chirp leading to an improved digital transmission [90], a significant increase in the modulation frequency response [91] and greatly reduced nonlinear distortion [91].…”

Characteristics of microwave photonic signal generation using vertical-cavity surface-emitting lasers with optical injection and feedback

“…Obviously, a microwave photonic signal can be generated by utilizing the beating of the two dominant frequencies in the P1 dynamic. Compared to other techniques, microwave photonic signal generation based on P1 oscillation has many advantages, such as a nearly single sideband (SSB) spectrum, low cost, all-optical components configuration, and widely tunable microwave frequency far from its relaxation resonance frequency [8], [9]. Microwave photonic signal generation based on P1 oscillation has mainly been investigated in distributed feedback (DFB) lasers [4], [7], [9], [10].…”

Enhancement in microwave modulation efficiency of vertical cavity surface-emitting laser by optical feedback

“…9,11 With injection locking, however, the frequency response of the laser is extended to higher frequencies and the overall response is flattened, rather than enhancing the frequency response at a particular rf frequency. The method is based on a relatively weak feedback from an external feedback cavity for the VCSEL, with the external cavity mode spacing corresponding to the desired modulation frequency.…”