High-speed vertical-cavity surface-emitting lasers (VCSELs) are essential for future data communications with high speed, low cost, and low power consumptions. For exceeding intrinsic modulation bandwidth of VCSELs limited by the relaxation oscillation frequency, manipulation of electron spin polarizations in VCSELs has been attracting attention in recent years. In this study, we theoretically and experimentally investigate modulation characteristics of 1.55-m VCSELs under the spin polarization modulation to obtaining tailored modulation characteristics suitable for high-speed data communications. Spin-flip rate equation analyses reveal that a short spin relaxation time is suitable for a flat modulation response under the spin polarization modulation, and a 100-Gb/s operation is expected in InAlGaAs quantum well (QW) VCSELs with a spin relaxation time of 10 ps, linear birefringence of 100 GHz, and dichroism of 50 GHz. A wide 3-dB bandwidth of 23 GHz determined by a frequency split between two orthogonal polarization modes (~19.4 GHz) is experimentally confirmed under optical spin polarization modulations by using a commercially-available InAlGaAs QW VCSEL whose relaxation oscillation frequency is ~3 GHz. These results support the idea that the ultrahigh- speed optical signal generation is available at the telecom wavelength of 1.55 m by applying the spin polarization modulation to VCSELs. Additionally, a modulation format conversion technique for output lights from the polarization modulation to phase modulation by using a polarizer is suggested and confirmed by the spin-flip rate equation analyses.
Phase noise of a single mode semiconductor laser is reduced drastically by introducing a newly proposed optical negative feedback scheme. Proof-of-concept experiment confirms that the spectral linewidth of a semiconductor laser can be reduced to 1/1,000 successfully by applying the scheme.
We propose a novel InP-based traveling-wave electrode Mach-Zehnder modulator. It has an n-i-n isotype heterostructure to reduce both electrical signal loss and the optical loss caused by the <i>p</i>- type cladding layer. This device provides a large modulation bandwidth of more than 40 GHz. We have also developed a compact
push-pull driven modulator module. We obtained error-free operation for a 40-Gbit/s NRZ signal in a push-pull configuration with a very low driving voltage of 1.3 V<sub>pp</sub>. We also confirmed that the modulator has low chirp characteristics by demonstrating a 100-km SMF transmission with a penalty of less than 1.5 dB for a 10-Gbit/s NRZ signal.
A monolithically integrated opto-electronic device is proposed as a fast wavelength-switching light source. This tunable duplex integrated light source comprises two wavelength-tunable distributed Bragg reflector (DBR) laser diodes (LDs), two MQW-electro-absorption optical switches, a Y-shaped waveguide coupler, a MQW-electro-absorption modulator, and two thermal drift compensators (TDCs). The wavelength-switching time of the optical switches was estimated to be 60 ps including a 50-ps rise time for the electrical-pulse generator. The wavelength of a 10-Gbit/s NRZ-modulated optical signal can be switched without bit loss. The function of the TDCs is to keep the device-chip temperature constant. Thermal-transient- induced wavelength drift with a millisecond-order time constant, which has been reported for DBR-LDs, and thermal crosstalk between the tuning regions of the integrated LDs, which causes wavelength fluctuation, are effectively suppressed by thermal-drift-compensation operation using the TDCs.
Conference Committee Involvement (2)
Active and Passive Optical Components for Communications VII
11 September 2007 | Boston, MA, United States
Active and Passive Optical Components for Communications VI
3 October 2006 | Boston, Massachusetts, United States