High efficiency resonant cavity microwave optical modulator

Generation of broadband laser by high-frequency bulk phase modulator with multipass configuration

A new technique is presented for obtaining a large broadband nanosecond-laser pulse. This technique is based on multipass phase modulation of a single-frequency nanosecond-laser pulse from the integrated front-end source, and it is able to shape the temporal profile of the pulse arbitrarily, making this approach attractive for high-energy-density physical experiments in current laser fusion facilities. Two kinds of cavity configuration for multipass modulation are proposed, and the performances of both of them are discussed theoretically in detail for the first time to our knowledge. Simulation results show that the bandwidth of the generated laser pulse by this approach can achieve more than 100 nm in principle if adjustment accuracy of the time interval between contiguous passes is controlled within 0.1% of a microwave period. In our preliminary experiment, a 2 ns laser pulse with 1.35-nm bandwidth in 1053 nm is produced via this technique, which agrees well with the theoretical result. Owing to an all-solid-state structure, the energy of the pulse achieves 25 μJ. In the future, with energy compensation and spectrum filtering, this technique is expected to generate a nanosecond-laser pulse of 3 nm or above bandwidth with energy of about 100 μJ.

Efficient, high-frequency bulk phase modulator

An efficient, 10.4-GHz bulk phase modulator is demonstrated that produces frequency-modulated optical bandwidths in excess of 300 GHz in a double-pass configuration with modest microwave drive power. The waveguide resonator design employs velocity matching to maximize phase-modulation efficiency and a modified form of cutoff waveguide coupling to achieve a high microwave cavity Q factor that reduces power requirements. The measured microwave performance of the modulator agrees well with performance predicted from fully anisotropic, three-dimensional numerical simulations.

Resonantly enhanced radio frequency electrooptic phase modulator

We have designed and fabricated a new type of resonant electrooptic phase modulator. With this device, the rf power required to produce the same modulation index as that obtained from the conventional traveling wave design can be reduced by as much as 3 dB. The peak modulation response can be controlled from ~150 to 350 MHz by varying the value of an externally loaded surface mount inductor. The resonant device may be modeled as a lumped-element bandpass filter. Results of the experimental characterization show excellent agreement with the model.

High frequency Fabry-Perot phase modulator

We have constructed an efficient high frequency phase modulator using a KDP crystal modulator in a Fabry-Perot interferometer. We present the theoretical analysis for the performance of such a modulator and compare this with experimental results. We have obtained a modulation index of 0.6 at 2.7 GHz with 0.3 W of microwave power. This implies that the use of a Fabry-Perot cavity can reduce the amount of drive power needed to achieve a given modulation index by 3 orders of magnitude or more. Such a device is particularly useful in the ultraviolet region of the spectrum where one must use relatively inefficient modulator crystals.