Ultrafast all-optical deflection based on an induced area modulation in nonlinear materials

Solid-state ultrafast all-optical streak camera enabling high-dynamic-range picosecond recording

We demonstrate an ultrafast optical recording system based on a novel optical beam deflection technique. An optical pump temporarily creates an array of prisms that deflect an optical signal beam within a GaAs/AlGaAs planar waveguide. The fabricated device yielded, to our knowledge, the fastest sustained optical deflection reported to date and was used to create spatial representations of ultrafast temporal waveforms. A conventional camera was then used to record single-shot waveforms with a 2.5 ps resolution over a 50 ps record with a dynamic range in excess of 3000:1. Through further development, this all-optical streak camera could provide insight into previously unmeasurable phenomena in many fields.

Nonlinear photonic structures for all-optical deflection

We present a new type of photonic structures in quadratic nonlinear materials that enable efficient and continuous all-optical deflection. The structures are based on two-dimensional modulation of the nonlinear coefficient and consist of a set of symmetric or anti-symmetric arcs that form a periodic pattern in the propagation direction and a chirped pattern in the transverse direction. Stoichiometric lithium tantalite structures were tested by second harmonic generation. Varying the pump wavelength from 1545 nm to 1536 nm resulted in continuous angular deflection of the second harmonic wave up to approximately 2.3 degrees . Continuous deflection was also obtained by varying the crystal temperature at a fixed pump wavelength.

Ultrafast deflection of spatial solitons in AlxGa(1-x)As slab waveguides

We demonstrate ultrafast all-optical deflection of spatial solitons in an AlxGa(1-x)As slab waveguide, using 190 fs, 1550 nm pulses to generate and deflect the spatial soliton. The steering beam is focused onto the top of the waveguide near the soliton pathway, and the soliton is steered by refractive-index changes induced by optical Kerr, or free-carrier (Drude), effects. Angular deflections up to 8 mrad are observed.

Ultrafast transient Kerr lens in solution detected by the dual-beam thermal-lens method

Time profiles of a transient lens on a subpicosecond time scale are observed by use of a dual-beam thermal-lens configuration. On this time scale and under nonresonant conditions the transient lens is composed mainly of the Kerr response. The electronic and nuclear responses are clearly separated by the polarization selection.

Amplitude modulation and beam-steering properties of active binary phase gratings with reconfigurable absorption areas

By combining a binary phase grating and materials with a controllable absorption, it is shown theoretically that it is possible to modulate the light in a zero-order diffraction beam and that a high contrast level for the beam modulation can be obtained. The intensity of higher diffraction orders also changes, but it is calculated that high contrasts cannot be achieved for these higher-order beams with the active gratings that we examine. This specific modulator design that we use can be applied both for transmitted and for reflected light. Using the same ideas, one may build a beam-deflection device by varying the period of the grating by selectively changing the absorption levels in the grating. The deflection efficiency of the device can be improved compared with other designs by use of a grating with a reduced intensity of the nondeflected zero-order beam.

Steering of optical beams in nonlinear Kerr media by spatial phase modulation

A simple scheme to steer optical beams is proposed. The basic idea is to impose a sinusoidal phase modulation on the optical beam and then propagate it in a nonlinear Kerr medium. Spatial phase modulation splits the input beam into multiple subbeams, while the nonlinear medium shapes a particular subbeam into a spatial soliton in such a way that most of the beam power appears in a narrow beam whose direction can be controlled by changing the modulation parameters. We present numerical results showing how spatial phase modulation can be used to alter the path of an optical beam propagating in a nonlinear Kerr medium.

Induced focusing and spatial wave breaking from cross-phase modulation in a self-defocusing medium

The spatial effects of cross-phase modulation on a weak probe beam as it copropagates with an intense pump beam through a self-defocusing medium are investigated. Experimental results are presented that demonstrate induced focusing, beam deflection, and the spatial analog of optical wave breaking. The experimental results are in good qualitative agreement with theoretical predictions.