We reported the nonlinear properties of transfer curves of multiple quantum well (MQW) traveling-wave electroabsorption modulators (TW-EAMs) in analog optical link applications. A new method to extract the optical absorption coefficient of TW-EAMs was developed. By using the method, we investigated the dependence of the transfer curvs on both the input optical power and the bias voltage. The relationships between the RF output power and bias voltage as well as RF input power were studied experimentally and theoretically. A SFDR as high as 128 dB-Hz4/5 was successfully obtained by adjusting the bias level as well as optical input power at 10.0 GHz.
Electroabsorption modulators (EAMs) based on the quantum confined Stark effect have advantages in applications that require high speed, low drive voltage, and high extinction ratio. They are promising devices for external signal modulation in high-bandwidth optical communication systems. EAMs can be integrated with other devices like laser diodes, semiconductor optical amplifiers, and mode transformers. We have previously fabricated InGaAsP/InP multi-quantum well EAMs with a bandwidth of 25 GHz and a drive voltage of 1.2 V and 20 dB extinction ratio. Further optimization of our devices requires a detailed analysis of internal physical processes and their interaction. In this paper, we employ a two-dimensional electro-optic device model to analyze our EAMs. The model self-consistently combines kp bandstructure and absorption calculations with a carrier drift-diffusion model and optical waveguiding. The required low polarization sensitivity of EAMs leads to strong valence band mixing so that usual effective mass models cannot be applied. Optical transmission characteristics are calculated which are in good agreement with measurements. Modulation efficiency and linearity are analyzed in detail. Optimum operation voltages are identified.
Electroabsorption modulators (EAMs) based on the quantum confined Stark effect in multiple quantum wells (MQWs) have advantages for high-speed, low drive voltage, and high extinction ratio applications. In this paper, a traveling- wave electrode structure is proposed to achieve high bandwidths with long devices and lower drive voltages at 1.55 micrometers wavelength. An InGaAsP/InGaAsP MQW traveling-wave electroabsorption modulator (TWEAM) with a bandwidth above 20 GHz is fabricated. A drive voltage of 1.2 V for an extinction ratio of 20-dB is demonstrated. The effects of microwave transmission on the high-speed performance of TWEAMs are discussed. Successful data transmission experiments at 30 Gbit/s show a promising system performance of these devices. By using an integrated tandem TWEAM, pulse data transmission above 100 Gbit/s is achieved.
High speed, high efficiency, low noise and high saturation power are the characteristics desired for detectors in high bit-rate long-haul optical communication systems. We present the modeling of traveling-wave application photodetectors. These novel monolithic devices combine optical gain and absorption in a distributed fashion along a traveling-wave structure, providing high-responsivity and high-speed performance, without sacrificing saturation power. We present the models used to simulate the behavior of these devices, as well as their result. We show that TAP detectors have higher saturation power than other detectors with the same bandwidth-efficiency product, at the price of a small noise penalty, which is also calculated. The result is a net increase in the dynamic range.
GaAs-based high-speed photodetectors attract lots of attention in the past twenty years due to their maturity in material growth and processing. However their wide bandgap characteristic (830nm) restricts their applications in fiber communication wavelength (1.3(mu) m~1.55(mu) m). Recently some research groups had demonstrated GaAs-based n-i-n, p-i-in waveguide type photodetectors operating at 1.55 (mu) m by taking advantage of the mid-gap defect absorption of low- temperature grown GaAs (LTF-GaAs). In this paper we propose and analyze different bandwidth-limited factors for LTG-GAAs based metal-semiconductor-metal traveling wave photodetector (MSM TWPD) for both long and short wavelength cases. According to our calculation results, MSM TWPDs release the bandwidth limitation bottleneck in previous n-i-n and p-i-n TWPD structures, especially in the long wavelength case. Our analysis indicates that Lt-GaAs based traveling-wave photodetectors can offer excellent bandwidth as well as high saturation power performances in fiber communication wavelength, which corresponds to long absorption length regime.
In this work we report on 64 degree celsius continuous-wave operation of a 1.5 micrometer vertical cavity laser. This laser consists of two fused Al(Ga)As/GaAs mirrors with a strain-compensated InGaAsP/InP active region. Selective lateral oxidation is used for current confinement. Minimum room temperature threshold current is as low as 0.8 mA, and maximum cw output power is as high as 1 mW at 15 degrees Celsius. Pulsed operation is achieved up to 100 degrees Celsius.
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