B. K. Nayar

Experimental demonstration of optical soliton switching in an all-fiber nonlinear Sagnac interferometer

We demonstrate, for the first time to our knowledge, the switching of optical solitons. We observe switching of 93% of the total reflected energy in a partially transmitting integrated fiber loop mirror that makes up the interferometer. This result demonstrates the potential of solitons as the natural bits in ultrafast optical processing.

Two-wavelength operation of the nonlinear fiber loop mirror

We describe the two-wavelength operation of the nonlinear fiber loop mirror. In this mode of operation a high-power signal at one wavelength switches a low-power signal at another wavelength. This device is investigated both theoretically and experimentally. The experimental results show that the nonlinear loop mirror performs as an optical modulator that consists of all-fiber components.

Switch inversion and polarization sensitivity of the nonlinear-optical loop mirror

The switching characteristic of a nonlinear-optical loop mirror can be inverted by a birefringent bias element. The device reflectance is insensitive to polarization in the linear regime for arbitrary birefringence in the loop. Under certain conditions, birefringence leads to polarization sensitivity in the nonlinear regime, which is likely to be contributing to instabilities that have been observed recently in mode-locked fiber lasers.

All-optical switching in a 200-m twin-core fiber nonlinear Mach-Zehnder interferometer.

All-optical switching is demonstrated in a 200-m-long fiber nonlinear Mach-Zehnder interferometer. The only stabilization mechanism used is passive enclosure of the interferometer. Stable operation is obtained by using a twin-core fiber. The experiment demonstrates the feasibility of use of fiber nonlinear Mach-Zehnder interferometers for ultrafast switching and pipeline logic.

Monomode-polarization-maintaining fiber directional couplers.

The fabrication and experimental evaluation of monomode-fiber directional couplers having polarization-maintaining elliptical-cored fibers is described. The couplers have a polarization isolation of greater than 40 dB and insertion losses of less than 0.5 dB.

Organic second-order non-linear optical materials and devices

Organic second-order nonlinear materials are currently receiving considerable attention for fabrication of frequency mixing and electro-optic devices. In this paper the key concepts in the development of organic nonlinear materials and waveguide device design are introduced. The recent advances in nonlinear waveguides for frequency doubling and electro-optic devices are reviewed.

Polarization-desensitized liquid-crystal overlay optical-fiber modulator.

A fiber-based device with a novel nematic liquid-crystal overlay compatible with silica fiber at room temperature is reported here to demonstrate polarization-independent modulation. The device is formed using a polished half-coupler block that has been surface treated so that the liquid crystal affects orthogonal polarizations in a similar and simultaneous manner. This permits the modulation of input light of arbitrary polarization on the application of an electric field.

Amplification and second harmonic generation in non-linear fibre waveguides

Optical fibres with organic single-crystal cores offer the potential for efficient second harmonic generation (>50%) and high amplification gain (>35 dB) when centimetre-long devices are pumped by semiconductor lasers of just a few milliwatts of power output.

Design Of Efficient Organic Crystal Cored Fibres For Parametric Interactions: Phase Matching Requirements

There is an increasing interest in the fabrication of optical parametric devices, pumped by semiconductor laser diodes, for both generation and amplification of tunable coherent radiation. This can be achieved by using waveguiding structures as they permit high optical intensities with modest powers, long interaction lengths and phase-matching using modal dispersion. There have been reports on efficient three wave mixing processes in LiNbO3 waveguides but these require rather high power (>1W). The pump power required can be reduced by either increasing the interaction length or using materials with larger non-linearities. However, to date the maximum phase-matched interaction length has been limited to about 2cm4 in LiNbO3 waveguides due to non-uniformity of the waveguide.

Phase-Matched Optical Second Harmonic Generation in the Organic Crystal MBA-NP

Generation of tunable coherent radiation by three wave mixing in optical materials has, over the last decade, led to the search for highly nonlinear organic and inorganic materials. The ‘molecular engineering’ has resulted in the development of a number of organic materials with large nonlinearities and high optical damage thresholds{1}.