Measurement of small-signal and large-signal responses of packaged laser modules at high temperature

In this paper, the pulsed injection method is extended to measure the chip temperature of various packaged laser modules, such as the DFB laser modules, the FP laser modules, and the EML laser modules. An optimal injection condition is obtained by investigating the dependence of the lasing wavelength on the width and period of the injection pulse in a relatively wide temperature range. The small-signal frequency responses and large-signal performances of packaged laser modules at different chip temperature are measured. The adiabatic small-signal modulation characteristics of packaged LD are first extracted. In the large-signal measurement, the effects of chip temperature, bias current and driving signal on the performances of the laser modules are discussed. It has been found that the large-signal performances of the EML modules depend on the different red-shift speeds of the DFB and EAM sections as chip temperature varying, and the optimal characteristics may be achieved at higher temperature.

Characterization of parasitics in TO-packaged high-speed laser modules

An elaborate analysis of the parasitic network of high-speed through-hole packaging (TO)-type laser modules is presented using a small-signal equivalent circuit model. The intrinsic laser diode is obtained using the optical modulation technique, and is embedded into the model as a separate component. Three step-by-step measurements are made for determining the packaging parasitic network, including the test fixture, TO header, submount, bonding wire, and parasitics of the laser chip. A good agreement between simulated and measured results confirms the validation and accuracy of the characterization procedures. Furthermore, several key parasitic elements are found based on the simulation of the high-frequency responses of the packaged devices. It is expected that the 3-dB bandwidth of 12 GHz or more of the low-cost TO packaged laser module may be achieved using the proposed optimization method.

Potential frequency bandwidth estimation of TO packaging techniques for photodiode modules

Scattering parameters of photodiode chip, TO header and TO packaged module are measured, and the effects of TO packaging network on the high-frequency response of photodiode are investigated. Based on the analysis, the potential bandwidth of TO packaging techniques is estimated from the scattering parameters of the TO packaging network. Another method for estimating the potential bandwidth from the equivalent circuit for the TO packaged photodiode model is also presented. The results obtained using both methods show that the TO packaging techniques used in the experiments can potentially achieve a frequency bandwidth of 22 GHz.

SOI-based 16x16 thermo-optic waveguide switch matrix

A 16 x 16 thermo-optic wavelenght switch matrix has been designed and febricated on silicon-on-insulator wafer. For reducing device lenght, blocking switch matrix configuration is chosen. The building block of a matix is a 2 x 2 cell with Mach-Zehnder interferometer configuration, where a multi-mode interferometer serves as splitters/combiners. Spot size converters and isolating grooves are integrated on the same chip to reduce loss and power consumption. Average power consumption of the switch cell is 220 mW. The switching time of a switch cell is less than 3 mu s.

A novel fast lock-in phase-locked loop frequency synthesizer with direct frequency presetting circuit

This paper proposes a novel, fast lock-in, phase-locked loop (PLL) frequency synthesizer. The synthesizer includes a novel mixed-signal voltage-controlled oscillator (VCO) with a direct frequency presetting circuit. The frequency presetting circuit can greatly speed up the lock-in process by accurately the presetting oscillation frequency of the VCO. We fully integrated the synthesizer in standard 0.35 mu m, 3.3 V complementary metal-oxide-semiconductors (CMOS) process. The entire chip area is only 0.4 mm(2). The measured results demonstrate that the synthesizer can speed up the lock-in process significantly and the lock-in time is less than 10 mu s over the entire oscillation frequency range. The measured phase noise of the synthesizer is -85 dBc/Hz at 10 kHz offset. The synthesizer avoids the tradeoff between the lock-in speed and the phase noise/spurs. The synthesizer monitors the chip temperature and automatically compensates for the variation in frequency with temperature.

Monolithic integration of electroabsorption modulator and DFB laser for 10-Gb/s transmission

A strained InGaAsP-InP multiple-quantum-well DFB laser monolithically integrated with electroabsorption modulator by ultra-low-pressure (22 mbar) selective-area-growth is presented. The integrated chip exhibits superior characteristics, such as low threshold current of 19 mA, single-mode operation around 1550 nm range with side-mode suppression ratio over 40 dB, and larger than 16 dB extinction ratio when coupled into a single-mode fiber. More than 10 GHz modulation bandwidth is also achieved. After packaged in a compact module, the device successfully performs 10-Gb/s NRZ transmission experiments through 53.3 km of standard fiber with 8.7 dB dynamic extinction ratio. A receiver sensitivity of -18.9 dBm at bit-error-rate of 10(-1)0 is confirmed. (c) 2005 Elsevier B.V. All rights reserved.

Electroabsoorption-modulated laser light-source module using selective area growth for 10 Gb/s transmission

In this work, a novel light source of strained InGaAsP/InGaAsP MQW EAM monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 x 10(2) Pa) selective area growth ( SAG) MOCVD technique. Superior device performances have been obtained, sue h as low threshold current of 19 mA, output light power of about 7 mW, and over 16 dB extinction ratio at 5 V applied voltage when coupled into a single mode fiber. Over 10 GHz 3 dB bandwidth in EAM part is developed with a driving voltage of 3 V. After the chip is packaged into a 7-pin butterfly compact module, 10-Gb/s NRZ transmission experiments are successfully performed in standard fiber. A clearly-open eye diagram is achieved in the module output with over 8.3 dB dynamic extinction ratio. Power penalty less than 1.5 dB has been obtained after transmission through 53.3 km of standard fiber, which demonstrates that high-speed, low chirp EAM/DFB integrated light source can be obtained by ultra-low-pressure (22 x 102 Pa) SAG method.

Compact SOI arrayed waveguide grating demultiplexer with broad spectral response

A compact eight-channel flat spectral response arrayed waveguide grating (AWG) multiplexer based on siliconon-insulator (SOI) materials has been fabricated on the planar lightwave circuit (PLC). The 1-dB bandwidth of 48 GHz and 3-dB bandwidth of 69 GHz are obtained for the 100 GHz channel spacing. Not only non-adjacent crosstalk but also adjacent crosstalk are less than -25 dB. The on-chip propagation loss range is from 3.5 to 3.9 dB, and the 2 total device size is 1.5 x 1.0 cm(2). (c) 2005 Elsevier B.V. All rights reserved.

Scattering-parameter measurements of laser diodes

An accurate and simple technique for measuring the input reflection coefficient and the frequency response of semiconductor laser diode chips is proposed and demonstrated. All the packaging parasitics could be obtained accurately using a calibrated probe, and the impedance of the intrinsic diode chip is deduced from the directly measured reflection coefficient. The directly measured impedance of a laser diode is affected strongly by the short bond wire. In the frequency response (S(2)1) measurements of semiconductor laser diode chips, the test fixture consists of a microwave probe, a submount, and a bond wire. The S-parameters of the probe could be determined using the short-open-match (SOM) method. Both the attenuation and the reflection of the test fixture have a strong influence on the directly measured frequency response, and in our proposed technique, the effect of test fixture is completely removed.

Fabrication of 4 x 4 tapered MMI coupler with large cross section

MMI coupler with large cross section has low coupling loss between the device and fiber. However, large chip area is required. Recently proposed N x N tapered MMI coupler shows a substantial reduction in device geometry. No such kind of devices with N > 2 has yet been realized up to now. The authors have demonstrated a 4 x 4 parabolically tapered MMI coupler with large cross section that can match the SM fiber in silicon-on-insulator (SOI) technology. The device exhibits a minimum uniformity of 0.36 dB and excess loss of 3.7 dB, It represents a key component for realization of MMI-based silicon integrated optical circuit technology.

Effective method for evaluation of semiconductor laser quality

The measurements of one hundred 1.3 mu m planar buried crescent (PBC) structure InGaAsP/InP lasers demonstrate that parameters given by the electrical derivative of varied temperature and the variation of the parameters with temperature can be used to appraise the quality and reliability of semiconductor lasers effectual. By measurement of electrical derivative curves one can evaluate the quality of epitaxial wafer and chip, find the problems in the material and the technology, offer the useful information on increasing the quality and improving the technology of devices. (C) 2000 Elsevier Science Ltd. All rights reserved.

High efficiency fiber to waveguide optical coupler in silicon-on-insulator-based slot waveguides - art. no. 68310R

We propose a novel optical fiber-to-waveguide coupler for integrated optical circuits. The proper materials and structural parameters of the coupler, which is based on a slot waveguide, are carefully analyzed using a full-vectorial three dimensional mode solver. Because the effective refractive index of the mode in a silicon-on-insulator-based slot waveguide can be extremely close to that of the fiber, a highly efficient fiber-to-waveguide coupling application can be realized. For a TE-like mode, the calculated minimum mismatch loss is about 1.8dB at 1550nm, and the mode conversion loss can be less than 0.5dB. The discussion of the present state-of-the-art is also involved. The proposed coupler can be used in chip-to-chip communication.

Optimized design on high-power GaN-based Micro-LEDs - art. no. 684108

The structure of micro-LEDs was optimized designed. Optical, electrical and thermal characteristics of micro-LEDs were improved. The optimized design make micro-LEDs suitable for high-power device. The light extraction efficiency of micro-LEDs was analyzed by the means of ray tracing. The results shows that increasing the inclination angle of sidewall and height of mesa, and reducing the absorption of p and n electrode can enhance the light extraction efficiency of micro-LEDs. Furthermore, the total light output power can be boosted by increasing the density of micro-structures on the device. The high-power flip-chip micro-LEDs were fabricated, which has higher quantum efficiency than conventional BALED's. When the number of microstructure in micro-LEDs was increased by 57%, the light output power was enhanced 24%. Light output power is 82.88mW at the current of 350mA and saturation current is up to 800mA, all of these are better than BALED which was fabricated in the same epitaxial wafer. The IN characteristics of micro-LEDs are almost identical to BALED.

The effects of sapphire substrates processes to the LED efficiency - art. no. 68410M

We investigate the relation between the thickness of sapphire substrates and the extraction efficiency of LED. The increasing about 5% was observed in the simulations and experiments when the sapphire thickness changed from 100um to 200um. But the output power increasing is inconspicuous when the thickness is more than 200um. The structure on bottom face of sapphire substrates can enhance the extraction efficiency of GaN-based LED, too. The difference of output power between the flip-chip LED with smooth bottom surface and the LED with roughness bottom surface is about 50%, where only a common sapphire grinding process is used. But for those LEDs grown on patterned sapphire substrate the difference is only about 10%. Another kind of periodic pattern on the bottom of sapphire is fabricated by the dry etch method, and the output of the back-etched LEDs is improved about 50% than a common. case.

A 10-bit 2GHz current-steering CMOS D/A converter

This paper presents a 2GS/s 10-bit CMOS digital-to-analog converter (DAC). This DAC consists of a unit current-cell matrix for 6MSBs and another unit current-cell matrix for 4LSBs, trading off between the precision and size of the chip. The Current Mode Logic (CML) is used to ensure high speed, and a double Centro-symmetric current matrix is designed by the Q(2) random walk strategy in order to ensure the linearity of the DAC. The DAC occupies 2.2 x 2.2 mm2 of die area, and consumes 790mw at a single 3.3V power supply.