Adiabatic couplers: design rules and optimization

Explicit analytic design rules are derived for both 3 dB and full adiabatic couplers. The design rules are in excellent agreement with numerical calculations using the beam propagation method (BPM). It is shown that the length scaling for 3 dB couplers compared to full couplers makes the former more difficult to design. The design for each case is optimized to obtain the upper limit of performance and a comparison is carried out between two different design geometries for both 3 dB and full adiabatic couplers     

Metal-atom resonance-line lasers

UV photodissociation of alkali and group IIIa metal halides provides a simple, practical means of producing metal-atom resonance-line lasers. These lasers are useful for applications in remote sensing of the same metal atoms. A study of the laser physics of these devices provides basic physical information on the photodissociation of metal halides.     

A bidirectional beam propagation method for multiple dielectricinterfaces

A novel approach to the bidirectional beam propagation method, which can treat multiple dielectric interfaces, is developed and implemented using iterative methods. Comparisons with two previously published results demonstrate its accuracy, as well as its efficiency in computation time and memory. Finally, its capability in simulating and designing complex structures is also demonstrated via a three-channel add-drop multiplexer     

Low-voltage tunable TE/TM converter on ion-sliced lithium niobate thin film

Lift-off of a prefabricated thin-film lithium niobate device using ion slicing has been demonstrated. The device is a low-voltage electro-optically tunable TE/TM mode converter, which is fabricated on a sliced 10 /spl mu/m-thick film. A new electrode configuration allows this thin-film device low-voltage tuning of the mode conversion wavelength at 0.26 nm/V. The high tuning per volt is attributed to an improved overlap integral in the thin-film form of the device.     

Integration of magnetooptical waveguides onto a III-V semiconductorsurface

Optical waveguides fabricated on a yttrium iron garnet (YIG) substrate are integrated onto a semiconductor surface by using ridge waveguides patterned onto a prefabricated recess in the YIG surface. The recess separates the waveguides from the semiconductor substrate with an air-gap. This structure makes it possible to avoid coupling light within the YIG waveguides into the semiconductor substrate which has a higher refractive index. The excess optical loss due to the coupling can be as low as ⩽0.1 dB/cm with a 1-μm-wide air-gap. The calculated coupling loss is confirmed by comparing the guided TE and TM modes     

A low-loss and compact waveguide Y-branch using refractive-index tapering

A new approach to an integrated Y-branch power splitter, useful for strongly guiding waveguide circuits, is proposed, fabricated and tested. The device uses adiabatic mode evolution by effective-refractive-index tapering to achieve a compact, low-loss geometry. Device performance is examined numerically by twoand three-dimensional beam propagation simulations. Y-branches with an overall length of /spl sim/330 /spl mu/m and losses of <0.2 dB are then fabricated in GaAs-AlGaAs. A compact and low-loss 1/spl times/4 power splitter incorporating this Y-branch is also described and demonstrated.     

An integrated two-stage cascaded Mach-Zehnder device in GaAs

An integrated, cascaded, asymmetric GaAs-AlGaAs Mach-Zehnder (MZ) interferometer, for use in wavelength filtering and time-domain multiplexing, has been designed, fabricated, and tested, This device employs several new passive components, including height-tapered Y-branches, for uniform splitting and recombining, and index-tailored waveguide bends, for low-loss operation. The waveguide bend is designed with a predistorted index profile for minimizing both transition loss and radiation loss. The circuit is fabricated with a resistless, light-induced local etching technique, which enables rapid iterative fabrication of the device geometry to achieve the desired operating path delays. Acting as a wavelength filter, the fabricated device has a -24.3 dB minimum-to-maximum extinction ratio and a -10.5 dB side-lobe suppression ratio. Acting as a pulse-rate multiplexer, the device generates a four-pulse train with a 10-ps pulse-to-pulse separation and an amplitude uniformity of 80% for each input pulse