HYbrid Polarisation controlled and mOnolithic tunable vertical Cavity surface emitting lAsers, for eMbedded and comPact optical and microwave systems – HYPOCAMP

The HYPOCAMP project aims at developing a new concept of tunable lasers, compact and robust, potentially low cost, with a low power consumption, and benefiting from an important wavelength accuracy : in agreement with most of the prerequisite for mobile and embedded applications. The proposed device is based on the integration of a liquid crystal (LC) electro-optical layer, presenting an important optical index variation, inside a vertical (external) cavity surface emitting lasers (V(E)CSEL). The potentials of such LC technology enable to realize completely monolithic device, with a large wavelength tuning, and without any movable parts. This last point is expected to increase the reliability of the process, the robustness of the fabricated device, and more importantly the laser wavelength stability. This makes the LC-V(E)CSEL concept very attractive compared to alternative approaches, mainly based on MEMS VCSEL technologies. In this last case, wavelength tuning is achieved through an electrostatic or thermal actuation of a mobile membrane. Despite the cost and process complexity, these technologies are still controversial in reliability and more important are expected to present excess noise related to the agile membrane.
In the HYPOCAMP project, objectives are to highlight the LC concept potentialities and reliability, with the realization of two 1.55 µm emitting V(E)CSEL devices on InP subtrates. The first one is an electrically pumped VCSEL, integrating a LC layer within the microcavity, to realize a wavelength tuning larger than 50 nm without mode hopping wavelength, a tuning frequency exceeding 1 kHz, and with a significant improvement in the wavelength stability (linewidth < 1 MHz). These devices will be tested to evidence their interests in mainly two different areas optical systems : civil applications by integrating LC-VCSELs in optical telecommunication network based on wavelength multiplexing (WDM) and in monitoring infrastructure deformations based on fiber bragg grating optical sensors; and also defence applications with the realization of tunable microwave notch filters based on optical means. The second device is a tunable and ultra stable laser emitter, dedicated to high resolution spectroscopy. It is based on the integration of the LC within a VECSEL long cavity (few cm), to conceive shot noise limited laser, presenting a narrow laser linewidth (< 10 kHz). Also, in order to match with LC requirements that involves the control of the VCSEL output polarization, in this project we will use an original and efficient approach based on quantum dashes nanostructures as being the active layers within the V(E)CSEL devices.
In this project, LC and semiconductor technologies will be both integrated in a hybrid device, which will enable the development of a unique know-how, paving the ways for new functionalities within micrometer sized devices. Apart from the 1.55 µm emitting tunable device demonstrations proposed in this project, and according to the LC optical transparency in the [0.5-2.5] µm wavelength range, this LC concept potentially targets other important applications. It can be transferred to any kind of material systems (InP, GaAs, GaSb, GaN…), covering thus general public applications (0.4-0.8 µm), medical applications with optical imaging (0.8-1.3 µm), industrial interests with gas sensors (1.4-2.5 µm) and military aspects with photonic microwave applications (1.55 µm).