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InAs/InGaAs quantum dot mode-locked lasers are fabricated and characterized. The modal gain as the saturable absorber voltage (SAV) changes is investigated. The ground state lasing dominates at low SAV, and excited state transition emerges when SAV increases.
In this paper, a bidirectional hybrid fiber amplifiers is proposed and experimentally demonstrated. The hybrid amplifiers include a C-band erbium-doped fiber amplifier (EDFA) and an L-band Raman fiber amplifier (RFA). A single-wavelength pump source at 1495 nm is pumped shared to both the EDFA and the RFA. Under the pump power of 500 mW, the average gains are about 11.3 dB for the C band EDFA and...
A Ku-band power amplifier is successfully developed with an internal-matched single chip 6mm AlGaN/GaN high electron mobility transistors (HEMTs). LCL network together with microstrip circuits are used to directly match the impedance of the 6mm GaN HEMTs to 50Ohm without using power combiner. Under the pulsed condition (100μs, 10%), the developed GaN HEMTs power amplifier delivers a 22W saturated...
A low noise amplifier with dB-linear variable gain has been designed and fabricated based on high performance SiGe HBT in this paper. Negative feedback technology has been adopted to change the transmission gain of HBT through variable resistance of a forward biased p-i-n diode in the feedback path. The simulation results and measurement results agree well in frequency of 1.8GHz for CDMA application...
This paper analyzes the inherent limitations of the magnitude response in non-negative impulse response (NNIR) systems that are not of the lowpass type. In particular, this work shows the importance of the frequency response around the point of zero frequency and its effect on the achievable gain increases at higher frequencies. The findings are shown to serve as a guiding principle for the design...
A fully differential 60 GHz three-stage transformer-coupled amplifier is designed and implemented in 65 nm digital CMOS process. On-chip transformers which offer DC biasing for individual stages, extra stabilization mechanisms, and simultaneous input/inter-stage/output matching networks are used to facilitate a compact circuit design. With a cascoded circuit configuration, the amplifier is tested...
This paper presents fundamental limitations imposed on the frequency response of a filter by a non-negative impulse response (NNIR). Several upper-bounds on power spectral attenuation/gain in linearly spaced frequency regions are derived. These upper-bounds serve as a guide in the design of NNIR filters.
This paper presents several fundamental frequency-domain bounds for a non-negative impulse response (NNIR) filter. Upper-bounds on power spectral attenuation and power spectral gain in geometrically spaced frequency regions are derived, when power spectral attenuation near frequency zero is limited. By analyzing the tightnesses of these bounds, the relationship between the maximally allowable power...
We show experimentally that helium ion implantation in silicon can reduce the optical loss from free carriers produced by two photon absorption and allow optical gain from cw pumped stimulated Raman scattering in silicon waveguides.
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