JaeHyuk Shin

0.3V drive voltage GaAs∕AlGaAs substrate removed Mach–Zehnder intensity modulators

Push-pull driven Mach–Zehnder intensity modulators with a record low drive voltage of 0.3V were realized in substrate removed very compact GaAs∕AlGaAs optical waveguides at 1.55μm. The modulator electrode is 7mm long, corresponding to a drive voltage length product of 0.21Vcm. The modulation is due to linear electro-optic and carrier depletion effects and has a high speed potential. The propagation loss was 8dB∕cm, making moderately long devices possible.

35-GHz Bandwidth, 5-V-cm Drive Voltage, Bulk GaAs Substrate Removed Electrooptic Modulators

Bulk GaAs-AlGaAs true push-pull electrooptic modulators with 5-V-cm Vpi and 35-GHz bandwidth were demonstrated using substrate removal techniques. The traveling wave electrodes showed almost no dispersion, making it ideal for broadband applications.

Novel T-rail electrodes for substrate removed low-voltage high-speed GaAs/AlGaAs electrooptic modulators

A novel traveling-wave electrode utilizing capacitively loaded T-rail elements was developed for low-voltage high-speed substrate-removed GaAs/AlGaAs electrooptic modulators. Electrodes with varying dimensions were fabricated and characterized. Electrode phase velocity, characteristic impedance, loss coefficient, and capacitive loading were extracted from the measured s-parameters up to 40 GHz. Electrode was also simulated using a finite-element solver. The measured and calculated electrode capacitance values were found to be in excellent agreement, showing that the electrode can be precisely designed. Approaches were outlined to provide a group velocity-matched very high-speed modulator electrode suitable for a low drive-voltage substrate-removed GaAs/AlGaAs electro-optic modulator

Conductor Loss of Capacitively Loaded Slow Wave Electrodes for High-Speed Photonic Devices

In this paper, analytical expressions are presented for the microwave attenuation of slow wave electrodes obtained by periodically loading a regular coplanar line with capacitive elements. Such electrodes are commonly used in III-V compound semiconductor electro-optic modulators and other traveling wave devices. These results are obtained by modifying the existing analytical loss expressions for regular coplanar lines based on physical arguments. The predictions of these expressions are compared with experimental results up to 35 GHz and agreement is found to be very good. Validity of this analysis is also discussed. It is found that the approach works very well for lines of practical interest. Hence, the proposed approach enables complete design of capacitively loaded slow wave electrodes by predicting the microwave loss with closed-form equations in addition to velocity and characteristic impedance.

Bulk Undoped GaAs–AlGaAs Substrate-Removed Electrooptic Modulators With 3.7-V-cm Drive Voltage at 1.55

Substrate removed bulk GaAs-AlGaAs electrooptic modulators with 3.7-V-cm drive voltage at 1.55 mum were realized. The 1.94-mum-thick undoped GaAs-AlGaAs epilayer removed from its substrate behaves as an electrooptic dielectric layer and has electrodes placed directly on both sides. This allows a very strong modulating electric field overlapping very well with the optical mode. The propagation loss in the presence of electrodes is less than 2.9dB/cm. There is very good agreement between the measured and simulated values

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Very compact GaAs/AlGaAs optical waveguides with propagation loss as low as 0.9 dB/cm at lambda=1.55 microm were demonstrated using substrate removal and evaporated Si for index loading. Loss components were identified and minimized through process and waveguide design. Process induced roughness contributed significantly to overall propagation loss. Therefore a low damage process in addition to proper waveguide design is needed for loss minimization.

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All-monolithic air-post index-guided vertical-cavity surface-emitting lasers have been demonstrated under pulsed electrical injection at room temperature. The structure grown in single step by metal-organic chemical vapor deposition employs InP lattice matched InAlAs/InAlGaAs Bragg mirrors and a 2/spl lambda/-thick periodic gain active region with 15 InGaAs quantum wells (QWs). We report threshold current characteristics of these devices grown on a 2-in wafer with wide emission wavelength range of 1.51/spl sim/1.59 /spl mu/m. For the devices larger than 30-/spl mu/m in diameter, we found the minimum threshold current density of /spl sim/2.93 kA/cm/sup 2/ at the emission wavelength of 1.57 /spl mu/m, corresponding to about 20 nm wavelength offset between photoluminescence peak of InGaAs QWs and resonant cavity wavelength.

Propagation loss study of very compact GaAs/AlGaAs substrate removed waveguides.

Substrate removed Mach-Zehnder electro-optic modulators with InGaAlAs/InAlAs MQW cores are reported. Devices have 0.36 V-cm drive voltage length product and 2 pF/cm capacitance making them suitable for very low voltage and wide bandwidth operation.

Pulse operation and threshold characteristics of 1.55-μm InAlGaAs-InAlAs VCSELs

Integration of traveling wave electrical drivers with wide bandwidth ultra-low Vpi substrate removed electro-optic modulators is studied. 1.5 mm long device with 0.1 V Vpi, 50 Omega input impedance and 15 GHz bandwidth seems possible.

InGaAlAs/InAlAs multi quantum well substrate removed electro-optic modulators

Substrate-removed bulk GaAs/AlGaAs electro-optic modulators with high-speed slow wave electrodes and bandwidths exceeding 40 GHz were fabricated. These devices have true push pull operation with adjustable chirp.