We present a new technique for measuring the intensity I(t) of optical pulses using a temporal optical system. A diffraction grating pair followed by a microwave-driven, optical phase modulator configured as a time lens is used to uniquely map the pulse shape from the time domain to the frequency domain, allowing measurement of the pulse shape with a spectrometer. We discuss the theory of operation and present experimental results illustrating 3 ps time resolution.
Microelectromechanical system (MEMS) technology, and surface micromachining in particular, have led to the development of miniaturized optical devices with a substantial impact in a large number of application areas. The reason is the unique MEMS characteristics that are advantageous in fabrication, systems integration, and operation of micro-optical systems. The precision mechanics of MEMS, microfabrication techniques, and optical functionality all make possible a wide variety of movable and tunable mirrors, lenses, filters, and other optical structures. In these systems, electrostatic, magnetic, thermal, and pneumatic actuators provide mechanical precision and control. The large number of electromagnetic modes that can be accommodated by beam-steering micromirrors and diffractive optical MEMS, combined with the precision of these types of elements, is utilized in fiber-optical switches and filters, including dispersion compensators. The potential to integrate optics with electronics and mechanics is a great advantage in biomedical instrumentation, where the integration of miniaturized optical detection systems with microfluidics enables smaller, faster, morefunctional, and cheaper systems. The precise dimensions and alignment of MEMS devices, combined with the mechanical stability that comes with miniaturization, make optical MEMS sensors well suited to a variety of challenging measurements. Micro-optical systems also benefit from the addition of nanostructures to the MEMS toolbox. Photonic crystals and microcavities, which represent the ultimate in miniaturized optical components, enable further scaling of optical MEMS.
A resonant microwave optical phase modulator in LiNbO3 with multiple passes, based on an off-axis path in a stable optical resonator, is demonstrated as a time-lens. With 1 W of cw microwave power at 5.2 GHz, 45 ps pulses at 1.06 μm were temporally focused to 6.7 ps (FWHM). Increasing the drive power to 13 W, at 10% duty cycle, produced 1.9 ps pulses. The aperture of the time-lens is about 31 ps. This is the first demonstration of a useful time-lens.
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