Control of dual-wavelength laser emission via optical feedback phase tuning

TL;DR

This paper presents a method to control dual-wavelength laser emission by tuning optical feedback phase, enabling selective amplitude control of two wavelengths with high extinction ratios, adaptable across platforms.

Contribution

The authors introduce a phase-controlled optical feedback technique to selectively balance dual-wavelength laser amplitudes, demonstrated on an InP platform with high extinction ratios.

Findings

Achieved up to 38.6 dB extinction ratio for 10 nm separation

Achieved up to 49 dB extinction ratio for 1 nm separation

Demonstrated adaptability to different wavelength separations

Abstract

We propose and demonstrate a technique to control the balance between the two amplitudes of a dual-wavelength laser based on a phase-controlled optical feedback. The feedback cavity length is adjusted to achieve a relative phase shift between the desired emission wavelengths, introducing a boost in gain for one wavelength while the other wavelength experiences additional losses. Tuning the optical feedback phase proves to be an effective way to control the gain and losses, and, thus, to select one or balance the amplitude of the two emission wavelengths. This concept can be easily adapted to any platform, wavelength range and wavelength separations providing that a sufficient carrier coupling and gain can be obtained for each mode. To demonstrate the feasibility and to evaluate the performance of this approach, we have implemented two dual-wavelength lasers with different spectral separations together with individual optical feedback loops onto a InP generic foundry platform emitting around 1550 nm. An electro-optical-phase-modulator is used to tune the feedback phase. With this single control parameter, we successfully achieved extinction ratios of up to 38.6 dB for a 10 nm wavelength separation and up to 49 dB for a 1 nm wavelength separation.