Up to 50% cw phase-conjugate reflectivity has been obtained with a 30-mW diode laser at 0.85 microm by means of resonant degenerate four-wave mixing on an optically thick, 1-mm-long Cs vapor cell. Self-oscillation of a Fabry-Perot cavity containing this Cs cell is demonstrated.
The work reported here demonstrates for the first time degenerate four wave mixing (DFWM) phase conjugation in cesium (Cs) atomic vapor. The strong, spectrally narrow transition of cesium at 852 nm gives conjugate reflectivities up to 154% with low pump beam powers. Temperature tuning of the DFWM response over a 30 GHz bandwidth is also demonstrated. An improved experimental design to determine the DFWM angular response shows a field-of-view of 20 mrad at the half response points. Self-focusing effects are observed to be similar to those in sodium vapor with an onset of increased conjugate divergence for reflectivities greater than about 25%.
Summary form only given. Optical phase conjugation through nearly degenerate four-wave mixing (NDFWM) in semiconductor lasers has attracted considerable attention since being first demonstrated by Nakajima and Frey (1985). Such interest arises due to the very high conjugate reflectivity of order 30-40 dB which can be achieved owing to the amplifying effect of the semiconductor gain medium and cavity enhancement of the mixing process. The paper is focused on an experimental study of NDFWM in a two-section single cavity Fabry-Perot (TSSC FP) laser diode for different probe injection powers. We present results on the conjugate reflectivity dependence of the frequency detuning subject to different injection power. It is shown that the conjugate reflectivity is dependent on optical probe injection into either section of a TSSC FP laser diode, injection power and bias current condition.
Recently, there has been increased interest in the use of resonant atomic systems for performing optical-wavefront conjugation. This interest has arisen because resonant systems are inherently fast, with response times in the nanosecond range. However, resonant systems tend to have lower efficiencies and greater optical power requirements than do photorefractive crystals, such as BaTiO3. In this paper, we explore the possibility of using a highly efficient Raman laser1 in a sodium-vapor cell to obtain efficient phase conjugation at greatly reduced optical power densities. In this demonstration we use a self-pumped (linear-cavity) conjugator for simplicity. With this setup, we have achieved phase- conjugate reflectivities of 2% with input powers of only 20 W/cm2. This is only 2% of the optical power density previously reported2 to obtain comparable reflectivity with a self-pumped scheme in sodium vapor.