Ultrafast two-photon nonlinearities in CdSe near 1.5 mu m studied by interferometric autocorrelation

We have used interferometric autocorrelation measurements to study the femtosecond nonlinear optical properties of bulk CdSe crystals in the wavelength region just above the half gap wavelength of 1.42 μm. Between 1.42 and 1.55 μm, we measured an ultrafast third-order nonlinearity with nonlinear refractive index n 2 = 1.3 × 10 -13 cm 2/W -1. Detailed modeling of the autocorrelations revealed the influence of higher order effects due to free carriers generated by nonlinear absorption. We find that CdSe is an interesting alternative material to AlGaAs for applications in this technologically important wavelength region

Photon-number squeezing in a free-running quantum-well laser operating at 980 nm

We present intensity noise investigations of a free-running InGaAs quantum-well laser diode operating at 980 nm at room temperature. The laser had a threshold current of 17 mA. Photon-number squeezing was achieved for drive currents of 48 mA when the laser was operating on two dominant longitudinal modes. The degree of squeezing obtained was 9%, which was in reasonable agreement with the current-to-current efficiency of 11%. No squeezing was observed at 35 K

Interferometric autocorrelation measurements of ultrafast two-photon nonlinearities in CdSe

Bulk crystals of CdSe are studied to verify it as an alternative to AlGaAs in the 1.5 μm wavelength due to its half-gap energy of 0.875 eV and large nonlinear figure of merit. The pulses transmitted to the crystal are characterized by interferometric autocorrelation and spectral analysis. Detailed numerical modeling are used to identify the contributions of the different effects. Femtosecond pulses from an optical parametric oscillator, operating between 1.4 and 1.6 μm, are used. The nonlinear refractive index of 1.3×10-13 cm2/W compares favorably to AlGaAs and is suitable for a number of nonlinear applications