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Description
This paper presents a development of an optical arrangement that captures photons traveling in the multi-pass fashion based on a so-called laser recirculation. An optical trapping scheme is relied on the principle of nonlinear frequency conversion. In this demonstration, a L-shape resonator performing as the master cavity provides a laser beam with a fundamental frequency to create the frequency-doubled photon. The frequency-doubled laser beam is trapped inside the slave cavity which is designed to be an off-axis resonator. A retroreflector allows the off-axis configuration of the slave cavity. The alignment and trip of the photons was governed by lenses and mirrors of the slave cavity. To prove this novel concept, the demonstration is achieved by using a Quasi-CW pumped Nd:YAG laser at 1064 nm. In the master cavity, this fundamental frequency beam is incident on a nonlinear crystal (OPO) placed inside the cavity to generate the frequency-doubled laser beam at 532 nm. The frequency-double laser beam is then trapped inside the slave cavity. The retroreflector controls the trajectory of such a beam. A lens telescope is placed inside the slave cavity to collimate the laser beam. Using this off-axis laser recirculation, the interference problem can be alleviated. The optical setup is also insensitive to environmental vibration that allows to be operated in a hostile environment. Using an optical ray tracing program, the effective mode volume for the slave cavity can be calculated. The simulation can also predict the maximum roundtrips for various situations. The off-axis laser recirculation shows the promise of the simple robust and reliable multi-pass optical cavity which is suitable for laser spectroscopy and optical switching applications.
