The existence of two polarization dependent band edges in InGaAs/InP quantum well material has been used to demonstrate single wavelength all-optical switching in a nonlinear guided wave Fabry–Perot resonator. The device had a single quantum well embedded in the optical waveguide and was characterized as a function of input pump power and laser wavelength using laser pulses of about 45 ps duration at a repetition rate of 82 MHz. A signal gain factor of over two was obtained for pump pulses of 1.2 pJ and the optimum operating wavelength of 1.51 μm was found to coincide with the heavy hole exciton absorption resonance.

Reported are measurements, in the 1.5 μm wavelength region, of the nonlinear refractive and absorptive changes, associated with real excitation processes, in a tensile-strained 6.7 nm thick In0.47Ga0.53As/InP single quantum well centred within a linear InGaAs/InP multiple quantum well waveguide Fabry-Pérot (PF) cavity. The refractive index changes were determined using two different pump/probe techniques: direct measurement of the refractive index changes in a FP cavity, and also via a Kramers-Kronig transformation of the absorption changes in the wavelength region of the bandgap resonance. Comparing these two measurements, reveals that there is a significant non-resonant contribution to the total refractive index changes in the SQW material, which is attributed to an enhanced free carrier absorption contribution due to carrier confinement in the two-dimensional quantum well. At wavelengths near the bandedge, index and absorption changes of Δn= -0.12 and Δα=8300 cm-1, respectively, were observed, while Δn=-0.07 was measured at a wavelength over 90 nm from the bandedge. These index changes are sufficient to allow the design of, polarisation independent, optical switches based on carrier induced refractive index changes such as bistable Fabry-Pérots, with predicted sub-mW switch powers.

The Gas Source MBE growth of high quality GalnAsP/InP Bragg reflector stacks for operation at 1.5μm followed by growth of an MOVPE AlInGaAs/InGaAs MQW structure is demonstrated. An asymmetric Fabry-Perot non-linear etalon structure was completed by dielectric mirror deposition. A clear bistable response was observed for the device as a function of incident light intensity, with low critical switching power (<1mW) and excellent thermal stability.

We report measurements of optically induced refractive index changes and their saturation, in an InGaAs single quantum well, centered within a linear multiple quantum well waveguide Fabry-Perot resonator using diode laser sources. A small-signal nonlinear refractive cross- section (sigma) n equals -8 X 10-20 cm3 was deduced for probe wavelengths near the TE absorption edge, and (sigma) n equals -4 X 10-20 cm3, 100 nm from the bandedge.

We report measurements of optically induced carrier-dependent refractive index changes and their saturation in an InGaAs single quantum well centered within a linear multiple quantum well guided-wave Fabry-Perot resonator using diode laser sources. A low-excitation nonlinear refractive cross-section sigma(n) = -1 X 10(-19) cm3 was deduced for probe wave-lengths near the TM absorption edge, falling only to sigma(n) = -3.1 X 10(-20) cm3, over 0.16 mum from the bandedge. For an incident irradiance of 18 kW/cm2 , refractive index changes in the InGaAs quantum well as large as -0.16 were deduced near the absorption edge, while the index change at a wavelength 0.16 mum from the absorption edge was -0.055. This large off-resonant index change is attributed to an enhanced free-carrier contribution within a 2-D system.

Measurements have been made at wavelengths between 1486 and 1600 nm of nonlinear refraction and absorption in an InGaAs single quantum well centered in an InGaAsP waveguide. Band-edge resonant nonlinear refractive cross sections as large as sigma(n) = -5.0 X 10(-20) cm3 have been deduced with a characteristic saturation carrier density of approximately 2 x 10(18) cm-3. For all pulse lengths used (less-than-or-equal-to 15 ms) the electronic transition nonlinearity appeared always to dominate any thermally induced refractive-index changes.

We report measurements of quasi-cw optical bistability in an InGaAs/InP multiple quantum well waveguide Fabry–Perot cavity at 1.47 μm wavelength. This operating wavelength is detuned from the band-edge resonance by 0.07 μm, where an enhanced free-carrier contribution to the nonlinear refractive index due to 2D confinement of carriers in the quantum wells accounts for the large index variations. The effect of any thermally induced nonlinear response is negligible.

The Letter reports the first demonstration of thermally stable, optical bistability in a passive InGaAs/InGaAlAs multiquantum well nonlinear Fabry-Perot etalon at the wavelength 1.5 μm. Critical switch powers of 1 mW were obtained, permitting operation with a CW diode laser source. Switch on/off times of 14 ns/40 ns were observed under slow ramping conditions.

The observation of submilliwatt switching and optical bistability in an InGaAs/InP MQW waveguide Fabry-Perot cavity using diode laser sources is reported. Second-order bistability was also observed, with a higher power colour-centre laser source, showing that optically-induced phase shifts of greater than 2x can be achieved at power levels of less than 5 mW. A switch contrast of approximately 3:1 was observed.

All-optical switching phenomena within a waveguide configuration are of considerable interest for routing and signal processing applications in communications systems. Two classes of device can be identified: those dependent on non-resonant ultrafast nonlinearities, capable of switching at the data-rate of ultra-high frequency signals; and those exploiting the much lower power resonant nonlinear phenomena which, due to their slower (> 100ps) response, are suitable as data-transparent switches capable of opening or closing the desired channels within a network under optical control.

We have measured the nonlinear refractive index, n2, and two-photon absorption coefficient, beta, in 4BCMU planar waveguides at 1.064 mum wavelength using picosecond pulses. We use a beam propagation code, with n2 and beta as fitting parameters, to make numerical comparison with the experimental data. Deduced values from this analysis are n2 = -1.5 x 10(-13) cm2W-1, confirming the negative sign of the nonlinearity at this wavelength, and beta = 0.01 cm MW-1.

Measurements have been made of the carrier lifetimes in MOCVD and MBE InGaAs quantum wells in a waveguide configuration using a CW probe and a picosecond pump at a wavelength of 1.5 mum. Values in the range 4-7 ns were obtained for excitation densities of the order of 3-6 x 10(17) cm-3.

The strong confinement of light in planar-optical waveguides has been used to measure the two-photon absorption coefficient, β, in 4-butoxycarbonylmethylurethane polydiacetylene (4BCMU) thin films. Prisms were used to couple the 30–60 ps pulses (up to 10 μJ) from a mode-locked YAG laser (λ=1.06 μm) into the thin-film waveguides. A simple analytical theory is compared with the experimental results to give a value of β≊4×10−3 cm/MW.

Semiconductor quantum-well structures can provide enhanced nonlinear effects compared to those observed in bulk material. The largest irradiance-induced refractive changes occur at wavelengths nearly resonant with the band edge or exciton absorption. If such a nonlinearity is to be effectively exploited in a waveguide configuration, the absorption due to the active quantum-well layers must be diluted to ensure sufficient transmission. Although this produces, all else being equal, a proportional drop in the effective nonlinearity (n2), it does permit operation at, or near to, the optimum wavelength where the figure-of-merit n 2 /α is maximized. In addition to the possible device potential of nonlinear optical waveguides, this configuration also permits investigation of the nonlinearity using light polarized both parallel (TE) and perpendicular (TM) to the quantum well. We present here measurements of nonlinear absorption and refraction, associated with electron-hole pair excitation, in an InGaAs Single Quantum Well (SQW) centered within a strip-loaded, non-absorbing InGaAsP waveguide.