Sub-cycle QAM modulation for VCSEL-based optical fiber links

QAM modulation utilizing subcarrier frequency lower than the symbol rate is both theoretically and experimentally investigated. High spectral efficiency and concentration of power in low frequencies make sub-cycle QAM signals attractive for optical fiber links with direct modulated light sources. Real-time generated 10-Gbps 4-level QAM signal in a 7.5-GHz bandwidth utilizing subcarrier frequency at a half symbol rate was successfully transmitted over 20-km SMF using an un-cooled 1.5-μm VCSEL. Only 2.5-dB fiber transmission power penalty was observed with no equalization applied

Inducing electron spin coherence in GaAs quantum well waveguides: Spin coherence without spin precession

Electron spin coherence is induced via light-hole transitions in a quantum well waveguide without either an external or internal DC magnetic field. In the absence of spin precession, the induced spin coherence is detected through effects of quantum interference in the spectral domain coherent nonlinear optical response. We interpret the experimental results qualitatively using a simple few-level model with only the optical transition selection rule as its basic ingredients

A Low-Power 1-Gb/s CMOS Laser Driver for a Zero-Bias Modulated Optical Transmitter

Abstract-We demonstrate the feasibility of using a CMOS laser driver for a low-power digital optical transmitter that is capable of at least 1-Gb/s operation. The transmitter employs low threshold lasers and zero-bias modulation. The circuit driver uses a strategy for low power consumption such that a majority of the total transmitter power is consumed by the laser instead of the electronics. The driver can function over a wide temperature range (77 K-300 K) for a variety of laser diodes

Site-Controlled Growth of Monolithic InGaAs/InP Quantum Well Nanopillar Lasers on Silicon

In this Letter, we report the site-controlledgrowth of InP nanolasers on a silicon substrate with patterned SiO2 nanomasks by low-temperature metal−organic chemicalvapor deposition, compatible with silicon complementary metal−oxide−semiconductor (CMOS) post-processing. A two-step growth procedure is presented to achieve smooth wurtzite faceting of vertical nanopillars. By incorporating InGaAs multiquantum wells, the nanopillar emission can be tuned over a wide spectral range. Enhanced quality factors of the intrinsic InP nanopillar cavities promote lasing at 0.87 and 1.21 μm, located within two important optical telecommunication bands. This is the first demonstration of a site-controlled III−V nanolaser monolithically integrated on silicon with a silicon-transparent emission wavelength, paving the way for energy-efficient on-chip optical links at typical telecommunication wavelengths