Search

We report on the small-signal high-frequency response of a GaNAsSb/GaAs pin waveguide photodetector at 1.55-μm wavelength. The GaNAsSb absorbing layer with 3.5% N and 18% Sb is sandwiched by GaAs-cladding layers. The device of an 8-μm ridge width and 15-μm ridge length has a dc responsivity of 0.44 A/W and an 11-GHz cutoff frequency at 5-mW optical illumination at a bias condition of -5 V. A higher cutoff frequency of 14.3-GHz is achieved on the smallest device of 4-μm ridge width and 17-μm ridge length with a responsivity of 0.2 A/W at a reverse bias condition of -1 V.

We describe the design, optimization and fabrication of side-illuminated p-i-n photodetectors, grown on InP substrate, suitable for surface hybrid integration in low-cost modules. The targeted functionalities of these photodetectors were a very high responsivity at 1.3- and 1.55-/spl mu/m wavelengths and quasi-independent on the optical polarization, and had a high alignment tolerance. Moreover, in order to avoid any reliability problem, the principle of evanescent coupling was adopted. Two photodetectors were optimized, fabricated, and tested; the first was for classical cleaved fiber, and the second was for lensed fiber. Because the considered epitaxial structures were complicated to optimize, the method of the genetic algorithm was used, associated with a beam propagation method (BPM). The photodetectors are based on multimode diluted waveguides, which are promising structures in the field of optoelectronics and integrated optics. Starting from the presented comparisons between experimental and theoretical results, the interest of the design method is discussed and the complete performances of newly fabricated devices are presented. The aspect of the cutoff frequency is also considered.

A three dimensions of semivectorial finite difference beam propagation method (FD-BPM) in cylindrical coordinates is investigated in order to analyze the optical wave propagation in the bent waveguides with the strong lateral confinement which will keep low radiation loss. The three dimensional (3D) semivectorial wave propagation equation is programmed in the quick and unconditionally stable procedure by using the alternating direction implicit method. This version of FD-BPM could well express the polarization characteristics of modal field near the dielectric interfaces and accurately simulate the wave propagation in bent waveguides even at a very small radius (

This letter demonstrates an evanescently coupled p-i-n photodiode combined with a multimode diluted waveguide using a simple all 2-in InP processing that includes on-wafer mirrors etching and antireflection coating. A high responsivity of 0.81 A/W at 1.55 mum with less than 0.4-dB polarization dependence and a large -1-dB vertical alignment tolerance of 2.70 mum were achieved simultaneously with a bandwidth of 47 GHz. Stable operation for over 1000 h was obtained under bias stress and temperature at 200degC

In this paper, we present a theoretical study and a numerical simulation of various long wavelength top-illuminated p-i-n photodetectors in the frequency range of 2.5-60 GHz under high optical modulated power at 1.55-/spl mu/m wavelength. The modeling includes a monodimensional drift-diffusion model for the device and takes into account the external circuit. We considered six InP/GaInAs/InP photodetectors especially designed to work at 2.5, 10, 20, 30, 40, and 60 GHz, respectively. For the one with the highest frequency, we intentionally sacrificed the quantum efficiency in order to compare them at the end with the results already obtained in the case of waveguide p-i-n photodetectors. The results show the maximum microwave-output power for each photodetector at its specific working frequency. Additionally, we present the effects of the modulation depth, the back illumination, and the wavelength of 1.3 /spl mu/m.

This letter demonstrates a new solution to achieve low-cost, highly integrated, and reliable InP-based p-i-n photodiodes for wavelength-division-multiplexing optical networks, absorbing 1.55-/spl mu/m wavelength and transparent to 1.3 /spl mu/m. It is based on a multimode diluted waveguide (MDW) combined with an evanescently coupled photodiode. The overall structure is optimized using a genetic algorithm linked to a beam propagation method software. The computed responsivity of the MDW photodiode is 0.86 A/W at 1.55 /spl mu/m, and the 1.3/1.55-/spl mu/m optical crosstalk is better than -20 dB (-40-dB electrical). The proposed device is designed for hybridization on silicon platform for low-cost modules, with potential application up to 10 Gb/s.

We have demonstrated a low-cost high-bandwidth and high-responsivity evanescent waveguide unitravelling-carrier photodiode (PD) fabricated using all 2-in InP processing including on-wafer mirrors and coating. Optimization of the optical input waveguide was made using the method of the genetic algorithm associated with a beam propagation method. Optical fiber coupling to the PD is based on a diluted multimode waveguide allowing simple material epitaxial growth. The fabricated PDs exhibit simultaneously 0.76-A/W responsivity at 1.55 /spl mu/m, >50-GHz bandwidth, and more than 22-mA average saturation photocurrent at 50 GHz. The light polarization dependence is less than 0.1 dB.

Using a 2-D bipolar physical model we highlight the main parameters that govern the long-wavelength MSM PD performance (cutoff frequency and responsivity). This covers applied potential, electrode spacing, absorbing layer thickness, and heterojunction effect. We also report that using a backside illumination technique and a thin absorbing layer we can reach a cutoff frequency as high as 65 GHz with a responsivity of 0.2 A/W. >

In this paper, the behavior under very high optical power of waveguide PIN photodetectors grown on InP substrate is simulated. The problem is solved using a pseudo-bidimensional drift-diffusion model which describes the electrical behavior of the device including the effects of the external circuit. The optical behavior of the device is analysed using FD 2D and 3D beam propagation method. First, we present the optical behavior of the device when the illumination conditions change. Influence of device structure, spot width, spot position and injection angle on the quantum efficiency of the photodetector is so studied. Second, the whole modeling is validated using experimental results given in the literature. Three typical multimode structures w hich allow a high cut-off frequency as well as a good responsivity are then modeled and compared. The smaller one has a cut-off frequency of 75 GHz in small signal conditions and the main effect decreasing the microwave output signal when the optical input power increases is the carrier effect in the depletion region of the photodetector. The maximum microwave power of each photodetector is calculated in typical conditions of use. >

A report on the theoretical study of an integrated waveguide/photodetector is presented. The optical modeling is presented of an integrated waveguide/photodetector based on the absorption of the evanescent optical field in an absorbing layer which is deposited on the waveguiding layer. From this modeling, the expression of the electron-hole pair generation rate for such a device is established. This result is applied to the calculation of the dynamic quantum efficiency of an integrated waveguide/p-i-n photodiode. The static and dynamic behaviors of GaInAs p-i-n photodiodes monolithically integrated on a classical N/sup -//n/sup +/ InP homostructure waveguide or on a GaInAsP/InP heterostructure waveguide are discussed, and optimized structures are pointed out. >

An improved time-domain beam propagation method based on the propagation of a quasi-rectangular pulse is proposed to analyze and optimize the integrated components in which wide-angle of diffraction or reflection of light are possible. This method can overcome the drawback due to the modification of short pulse during propagation and reflection induced by the numerical errors and slow-varying envelope approximation in the usual TD-BPM. After validating this method for a planar waveguide, three 90/spl deg/ reflections on micromirrors are simulated.

A numerical model of the surface roughness is simply implemented into the beam propagation method to estimate the radiation losses in integrated optics devices. In this model, the deviation variables of the surface stem from a random generation controlled by the distribution function, and the spacing of deviations on the surface is determined considering their correlation length. The radiation losses due to surface roughness for a planar waveguide are estimated through this model using the FD-BPM scheme and are favorably compared with the ones obtained by another method reported in literature. For a 45/spl deg/ self-aligned integrated mirror made on a dielectric waveguide, the calculated radiation losses agree well with the measured ones.

Microwave impedance matching networks have been, for the first time, monolithically integrated with GaInAs p-i-n photodiodes and GaInAsP buried ridge stripe structure lasers ( lambda =1.3 mu m), both on a semi-insulating InP substrate. The microwave power transfer optical links were compared using matched and unmatched devices. Compared to an unmatched link, an improvement of 11.4 dB at 5.6 GHz (600 MHz bandwidth) is obtained for the totally matched one; this result corresponds quite well to the theoretical prediction (12 dB at 6 GHz). >