M. L. Bortz

Annealed proton-exchanged LiNbO 3 waveguides

We report characterization of annealed proton-exchanged waveguides in LiNbO(3). Effective-mode indices and fundamental-mode intensity profiles were measured for a variety of fabrication conditions. Index profile, depth, and surface refractive-index change were determined versus exchange depth and anneal time and are presented in a universal form. An empirical concentration-dependent diffusion model describing the annealing process is presented. The refractive-index dispersion in proton-exchanged and annealed proton-exchanged waveguides was determined for wavelengths between 0.4 and 1.1 microm.

Depth profiling of the d33 nonlinear coefficient in annealed proton exchanged LiNbO3 waveguides

We report depth profiling of the d33 nonlinear coefficient in annealed proton exchanged LiNbO3 waveguides using reflected second‐harmonic generation from angle‐lapped samples. At depths greater than the initial proton exchange depth the d33 coefficient retains nearly its bulk LiNbO3 value, but within the initial proton exchange region the value of d33 varies with annealing time. These results reconcile previous conflicting measurements of the d33 coefficient and explain the variation in the efficiency of guided wave frequency conversion devices with annealing.

Quasi-phase-matched optical parametric amplification and oscillation in periodically poled LiNbO 3 waveguides

We report quasi-phase-matched optical parametric amplification and oscillation in a periodically poled LiNbO(3) waveguide. Single-pass parametric gains of 4.1 dB, corresponding to 18%/W efficiency, were achieved at a signal wavelength of 1.55 microm with a pump wavelength of 782.2 nm. We formed a low-finesse cavity resonant at both signal and idler wavelengths by attaching mirrors to the waveguide end faces. Parametric oscillation was observed at wavelengths between 1.4 and 1.7 microm with a peak output power of 700 mW for pump wavelengths between 779 and 782 nm.

Infrared radiation generated by quasi‐phase‐matched difference‐frequency mixing in a periodically poled lithium niobate waveguide

We report quasi‐phase‐matched difference‐frequency generation of 2.1 μm radiation at room temperature using the d33 nonlinear coefficient in a periodically poled lithium niobate channel waveguide. A tunable Ti:Al2O3 laser (λ≊0.8 μm) and a Nd:YAG laser (λ=1.32 μm) were the pump and signal sources, respectively. With 160 mW of 0.81 μm and 1 mW of 1.32 μm radiation coupled into the waveguide, 1.8 μW of 2.1 μm radiation was generated, tunable over a 6 nm bandwidth. We also show that the annealed proton exchange process can change the shape of ferroelectric domains in lithium niobate.

Growth of alternating 〈100〉/〈111〉‐oriented II‐VI regions for quasi‐phase‐matched nonlinear optical devices on GaAs substrates

We present a technique for fabricating laterally patterned 〈111〉 and 〈100〉‐oriented regions of CdTe on GaAs by metalorganic chemical vapor deposition. Patterning of the crystal orientation is important for quasi‐phase‐matched nonlinear optical frequency conversion in semiconductor waveguides. Scanning electron micrographs and x‐ray diffraction analysis are used to confirm the presence of 〈111〉/〈100〉 grating structures. The CdTe layer is shown to be a suitable template to pattern the orientation of subsequently grown wide‐band‐gap films of ZnSe and ZnTe.

Iodine spectroscopy and absolute frequency stabilization with the second harmonic of the 1319-nm Nd:YAG laser.

We have frequency doubled a 1319-nm Nd:YAG laser in a quasi-phase-matched LiNbO(3) waveguide and used the asymptotically equal to1-mW second-harmonic output to investigate the (127)I(2) transitions near 660 nm. We reached submegahertz laser-frequency stability at a (vacuum) wavelength of 1319.098 nm by locking the second harmonic to the center of the P(48)6-6 transition.

Surface-emitting second-harmonic generation in a semiconductor vertical resonator.

We experimentally demonstrate a 240-fold increase in the efficiency of an AlGaAs/ALAs surface-emitting second-harmonic generation device by embedding the waveguide core in a monolithic vertical resonant cavity. Calculations indicate that conversion efficiencies of several percent per watt for second-harmonic generation of green or blue light may be expected in an optimized semiconductor resonant vertical-cavity surface emitter.

Measurement of the second-order nonlinear susceptibility of proton-exchanged LiNbO(3).

We have measured the d(33) nonlinear coefficient in proton-exchanged LiNbO(3) by using angle-dependent reflected second-harmonic generation and observed a reduction to </=1% of the bulk LiNbO(3) value.

Direct atomic flux measurement of electron-beam evaporated yttrium with a diode-laser-based atomic absorption monitor at 668 nm

A direct measurement of atomic flux in e-beam evaporated yttrium has been demonstrated with a diode-laser-based atomic absorption (AA) monitor at 668 nm. Atomic number density and velocity were measured through absorption and Doppler shift measurements to provide the atomic flux. The AA-based deposition rates were compared with independent quartz crystal monitors showing agreement between the two methods.

Demonstration of a vapor density monitoring system using UV radiation generated from quasi-phasematched SHG waveguide devices

Many industrial application require non-intrusive diagnostics for process monitoring and control. One example is the physical vapor deposition of titanium alloys. In this paper we present a system based on laser absorption spectroscopy for monitoring titanium vapor. Appropriate transitions for monitoring high rate vaporization of titanium require extension of available IR diode technology to the UV. The heart of this vapor density monitoring system is the 390 nm radiation generated from quasi-phase matched interactions within periodically poled waveguides. In this paper, key system components of a UV laser absorption spectroscopy based system specific for titanium density monitoring are described. Analysis is presented showing the minimum power levels necessary from the ultraviolet laser source. Performance data for prototype systems using second harmonic generation waveguide technology is presented. Application of this technology to other alloy density monitoring systems is discussed.