We present CW operation of a tunable InP based Vertical Cavity Surface Emitting Laser, integrating a liquid crystal micro-cell. In comparison with previous work, a larger 33 nm tuning and stable operation are obtained, according to major improvements presented in this paper.

An InP-based Vertical-Cavity Surface-Emitting Laser (VCSEL) with a liquid crystal (LC) microcell monolithically integrated on its surface for spectral tuning is investigated. Unlike tunable VCSELs integrating a movable membrane, here the physical length of the cavity remains unchanged and only the voltage applied on the LC ensures a refractive index modification for a particular polarization emitted by the VCSEL. This tunable VCSEL operates in CW at room temperature and exhibits more than 23 nm wavelength tuning around $1.55\mu \text{m}$ at a maximum applied voltage of 20 V. The measured laser threshold around 6.5 mW is still comparable to VCSEL without LC microcell, a clear indication that the optical losses related the LC are very low. On the other hand, for this first optically pumped device, the lasing characteristics suggest that the LC birefringence is lower than expected. To assess this hypothesis, thermo-optical simulations have been conducted.

Photonic devices with wavelength tuning capabilities are investigated with the use of liquid crystal microcells monolithically integrated onto the surfaces of photodiodes or VCSEL fabricated on InP based materials. For these two devices, we demonstrated that the detected or emitted wavelength can be selected on a tuning range of more than 70 nm in the case of the photodiode, and of more than 20 nm in the case of VCSEL.

A simple technology is demonstrated for the wafer-scale fabrication of liquid-crystal (LC) microcells that can be integrated in active optoelectronic devices. Fabrication of 1.55-mu m tunable Fabry-Perot optical micro-filter arrays is achieved owing to the insertion of a single nanoimprinted polymer grating dedicated to LC alignment and to the soft thermal transfer of a dry thick resist film between two highly reflective mirrors. The filter exhibits a spectral tuning range of 102 nm with only 18 V applied, as well as negligible internal loss, which makes it suitable for being inserted in a laser cavity. This constitutes a key step toward the large-scale integration of widely tunable photonic devices such as vertical-cavity surface-emitting lasers using LC technology.

In this work, we report InGaAs based photodiodes integrating liquid crystal (LC) microcells resonant microcavity on their surface. The LC microcavities monolithically integrated on the photodiodes act as a wavelength selective filter for the device. Photodetection measurements performed with a tunable laser operating in the telecom S and C bands demonstrated a wavelength sweep for the photodiode from 1480 nm to 1560 nm limited by the tuning range of the laser. This spectral window is covered with a LC driving voltage of 7V only, corresponding to extremely low power consumption. The average sensitivity over the whole spectral range is 0.4 A/W, slightly lower than 0.6 A/W for similar photodiodes that do not integrate such a LC tunable filter. The quality of the filter integrated onto the surfaces of the photodiodes is constant over a large tuning range (70 nm), showing a FWHM of 1.5 nm.