Stephan Schiller

82% Efficient continuous-wave frequency doubling of 1.06μm with a monolithic MgO:LiNbO 3 resonator

We describe a frequency-doubling monolithic standing-wave resonator made of MgO:LiNbO(3) with dielectric mirror coatings for impedance matching near 100 mW input power and near-optimum nonlinear coupling. An external conversion efficiency of 82% has been achieved.

Generation of strongly squeezed continuous-wave light at 1064 nm

A compact and effcient source of amplitude-squeezed light is described. It employs a semi-monolithic degenerate MgO:LiNbO(3) optical parametric amplifier pumped by a frequency-doubled Nd:YAG laser at 532 nm. Injection-seeding of the amplifier by a 1064 nm wave permits active stabilization of the cavity length and stable operation. At a pump power of 380 mW, a maximum noise reduction of 6.5 dB in the amplitude fluctuations of the 0.2 mW 1064 nm wave was detected. The average detected noise reduction in continuous operation over 14 minutes was 6.2 dB. Taking the detection effciency into account, this corresponds to a squeezing of 7.2 dB in the emitted wave.

Experimental studies of cryogenic optical resonators

We report on the development of optical resonators operated at cryogenic temperature. a miniature monolithic quartz crystal ring resonator has been operated at liquid helium temperature with a finesse of 330 at the Nd:YAG wavelength 1064 nm. A 3-cm-long Fabry_Perot cavity with mirrors optically contacted to a hollow fused silica spacer has been used for the frequency stabilization of two diode-pumped Nd:YAG lasers. The cavity exhibited a finesses of 240,000 at liquid helium temperature. The root Allan variance of the beat signal of the two lasers locked to two transverse modes of the cryogenic optical resonator (CORE) was below 10 Hz for integration times up to 100 s. Requirements for reaching sub-Hz instability for long times are briefly discussed and it is pointed out that COREs have interesting applications in high-precision fundamental physics experiments.

Generation of continuous-wave bright-squeezed light

We discuss different approaches to the generation of bright amplitude-squeezed light using second-order nonlinear effects in optical cavities. A 0.2 mW beam at 1064 nm exhibiting a 4 dB squeezing has been generated using a phase-sensitive type-I parametric amplifier pumped by frequency-doubled Nd:YAG laser. In applying frequency-doubling processes to the generation of amplitude-squeezed light, the appearance of parasitic parametric oscillation must be considered. This effect has been observed in a singly-resonant frequency doubler. We also describe recent developments in optical cavity design for doubly-resonant frequency doubling. Finally, we show theoretically that phase-mismatched second-harmonic generation in an optical cavity can be employed to generate a strong effective Kerr nonlinearity. This system appears promising for achieving optical bistability and for generating squeezed light of high power.