Femtosecond diode-based time lens laser for multiphoton microscopy.

We demonstrate a near-infrared, femtosecond, diode laser-based source with kW peak power for two-photon microscopy. At a wavelength of 976 nm, the system produces sub-ps pulses operating at a repetition rate of 10 MHz with kilowatt class peak powers suitable for deep tissue two-photon microscopy. The system, integrated with a laser-scanning microscope, images to a depth of 900 µm in a fixed sample of PLP-eGFP labeled mouse brain tissue. This represents a significant development that will lead to more efficient, compact, and accessible laser sources for biomedical imaging.

Control of the state of a mode-locked fiber laser using an intracavity Martinez compressor.

An intracavity Martinez compressor is incorporated into a fiber laser as a dispersion compensator and spectral filter. The Martinez compressor provides tunable dispersion from normal to anomalous. Inserting a mechanically adjustable slit into the compressor enables tunable spectral filtering independent of dispersion compensation. Mode-locking is achieved with laser bandwidths from 1.8 to 49.0 nm and compressor dispersions from +0.008 to -0.072 ps2. The laser generates stable pulses with 0.9 nJ pulse energy, a fundamental repetition rate of 77.5 MHz, and dechirped FWHM pulse widths as short as 82 fs.

Large extinction ratio optical electrowetting shutter.

A large extinction ratio optical shutter has been demonstrated using electrowetting liquids. The device is based on switching between a liquid-liquid interface curvature that produces total internal reflection and one that does not. The interface radius of curvature can be tuned continuously from 9 mm at 0 V to -45 mm at 26 V. Extinction ratios from 55.8 to 66.5 dB were measured. The device shows promise for ultracold chip-scale atomic clocks.

FPGA-based phase control of acousto-optic modulator Fourier synthesis system through gradient descent phase-locking algorithm.

We present a new application of the stochastic parallel gradient descent (SPGD) algorithm to fast active phase control in a Fourier synthesis system. Pulses (4.9 ns) with an 80 MHz repetition rate are generated by feedback from a single phase-sensitive metric. Phase control is applied via fast current modulation of a tapered amplifier using an SPGD algorithm realized on a field-programmable gate array (FPGA). The waveforms are maintained by constant active feedback from the FPGA. We also discuss the extension of this technique to many more semiconductor laser emitters in a diode laser array.