LIDARs are considered a key enabling technology for an array of applications in space, including celestial body approach, landing, rendezvous and docking, space debris identification and CubeSat constellations. Reliability, low cost and low size, weight and power (SWaP) are critical factors for these applications. Current spaceborne LIDAR systems are based on discrete optical components. These systems consume a lot of power and are bulky. In this work, a hybrid integrated (FMCW) LIDAR system operating at 1550 nm and based on an indium phosphide (InP) and silicon nitride (Si3N4) platform along with an external erbium-doped fiber amplifier (EDFA) compact module is proposed. By using a telecom-wavelength laser with an ultra-narrow linewidth of 1 kHz, and a 1D optical phased array (OPA) using lead zirconate titanate (PZT) phase shifters, the proposed PIC microlidar can operate up to 100 km. In order to realize small beam divergence, a 1x100 linear array consisting of 4 mm Si3N4 dual-layer grating antennas with a coupling efficiency of up to 80% of the incident power is utilized.
Pockels cell is one of the major components limiting the pulse repetition rate of high-power laser sources. The birefringence of the electro-optical crystal is controlled by the electric voltage which allows high-frequency modulation of intracavity losses, thus unlocking the MHz frequency band for pulse repetition rate. The purpose of this work was to investigate the influence of the piezoelectric ringing on the polarisation contrast of the potassium rubidium titanyl phosphate (KRTP) based electro-optical modulator in the frequency range up to 10 MHz. This was done by complex impedance and polarisation contrast measurements, as well as comparison to numerically identified fundamental frequencies of the crystal. The behaviour and dominant mechanism behind the effects of piezoelectric ringing were found to be distinct in three modulation frequency ranges: up to 2 MHz, above 2 MHz, and above 6.3 MHz. In particular, above 6.3 MHz, no piezoelectric-ringing-induced depolarisation was observed. These findings make KRTP based Pockels cells attractive for high-repetition-rate pulse picking applications.
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