High-performance circular TE/sub 01/-mode converter

This study presents the design and cold testing of a Ka-band TE/sub 01/-mode converter. A wave is efficiently converted from the TE/sub 10/ rectangular waveguide mode into the TE/sub 01/ circular waveguide mode. This converter comprises a power-dividing section and a mode-converting section. The field pattern and the working principle of each section are analyzed and discussed. A prototype was built and tested. Back-to-back transmission measurements exhibit excellent agreement to the results of computer simulations. The measured optimum transmissions are 97% with a 1-dB bandwidth of 5.8 GHz centered at 34.0 GHz. The angle-independent transmissions manifest high mode purity and the field pattern is directly demonstrated on a temperature-sensitive liquid-crystal sheet. In addition to exhibiting a high conversion efficiency, high mode purity, and broad bandwidth, this converter is also easy to construct and is structurally simple.     

The dV/dt capability of MOS-gated thyristors

In this paper, a detailed study of the dV/dt capability of MOS-gated thyristors is performed. It is shown that in addition to the conventional mode of dV/dt-induced turn-on in thyristors, termed the intrinsic mode, there exists another distinct mode of dV/dt-induced turn-on, peculiar to the MOS-gated thyristor structure, which the authors term the extrinsic dV/dt mode. The effective dV/dt capability is determined by both modes and is degraded by the presence of an external gate-cathode resistance and parasitic gate-anode capacitance. The existence of these two modes of dV/dt-induced turn-on is demonstrated experimentally, and the effect of device parameters on the dV/dt capability is studied     

Geiger mode operation of an In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode

Low-temperature photon counting with gated mode quenching is demonstrated with separate absorption, charge, and multiplication avalanche photodiodes that have an In/sub 0.52/Al/sub 0.48/As multiplication layer. A minimum of ten dark counts per second and single-photon detection efficiency of 16% were achieved at 130 K.     

An In0.52Al0.48As/n+-In0.53Ga0.47As MISFET with a modulation-doped channel

A heterostructure metal-insulator-semiconductor field-effect transistor (MISFET) with a modulation-doped channel is proposed. In this device, a very thin undoped subchannel is located between the undoped wide-bandgap insulator and a thin heavily doped channel. In the depletion mode of operation, electron transport takes place along the heavily doped channel. When the device enters the accumulation mode of operation, electrons pile up against the heterointerface in the high-mobility undoped subchannel. This results in markedly improved transport characteristics at the onset of accumulation. The concept is demonstrated in the In_0.52Al_0.48As/In_0.53 Ga_0.47As system on InP. A 1.5-μm-gate-length MISFET shows a unity current-gain cutoff frequency of 37 GHz     

Formation of reconfigurable singlemode channel waveguides in LiNbO/sub 3/ using spatial solitons

The formation of reconfigurable singlemode channel waveguides using photovoltaic dark spatial solitons is demonstrated in a titanium-diffused slab LiNbO/sub 3/ waveguide. The generated mode profile is shown to be influenced by the presence of titanium.     

A Fully Integrated Ultra-Low Insertion Loss T/R Switch for 802.11b/g/n Application in 90 nm CMOS Process

A 30 dBm ultra-low insertion loss CMOS transmit-receive switch fully integrated with an 802.11b/g/n transceiver front-end is demonstrated. The switch achieves an insertion loss of 0.4 dB in transmit mode and 0.1 dB in receive mode. The entire receiver chain from antenna to baseband output achieves a measured noise figure of 3.6 dB at 2.4 GHz. The switch has a P_1dB greater than 30 dBm by employing a substrate isolation technique without using deep n-well technology. The switch employs a 1.2 V supply and occupies 0.02 mm² of die area.     

TE Sub/011 Mode Sectorial Circular Cylindrical Cavities Filters

This paper presents a new cavity resonator for the TE /sub 011/ circular mode which allows a compact mechanical structure for a multiple-cavity filter and retains many electrical characteristics of larger filters. Theoretical values of Q are obtained, mode separation is demonstrated, and a 4-cavity experimental model with an elliptic transfer function is described.     

2.36 /spl mu/m diode pumped VCSEL operating at room temperature in continuous wave with circular TEM/sub 00/ output beam

Operation of a diode-pumped AlGaAsSb/GaInAsSb type-I quantum-well vertical cavity surface emitting laser emitting near 2.36 /spl mu/m is reported. The epitaxial structure, grown on GaSb by molecular beam epitaxy consists of a GaSb/AlAsSb Bragg reflector and a GaInAsSb/AlGaAsSb active region. A circular TEM/sub 00/ low-divergence laser operation is demonstrated in continuous-wave mode operation from 268 up to 308K. A threshold of 5.5 kW/cm/sup 2/ at 268K has been measured.     

Type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region

Operation of type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region has been demonstrated at temperatures up to 240 K in pulsed mode. These lasers fabricated with 150-/spl mu/m-wide mesa stripes operated in continuous-wave (CW) mode up to a maximum temperature of 110 K, with an output power exceeding 30 mW/f and a threshold current density of about 41 A/cm/sup 2/ at 90 K. The maximum CW operation temperature of 110 K is largely limited by the high specific thermal resistance of the 150-/spl mu/m-wide broad area lasers. A 20-/spl mu/m-wide mesa stripe laser was able to operate in CW mode at higher temperatures up to 125 K as a result of the reduced specific thermal resistance of a smaller device.     

Low-voltage tunable TE/TM converter on ion-sliced lithium niobate thin film

Lift-off of a prefabricated thin-film lithium niobate device using ion slicing has been demonstrated. The device is a low-voltage electro-optically tunable TE/TM mode converter, which is fabricated on a sliced 10 /spl mu/m-thick film. A new electrode configuration allows this thin-film device low-voltage tuning of the mode conversion wavelength at 0.26 nm/V. The high tuning per volt is attributed to an improved overlap integral in the thin-film form of the device.     

Study of chirp-free operation for guide/antiguide modulator

A method of achieving chirp-free operation of a field-induced guide/antiguide intensity modulator is reported. Both measured and calculated data for chirp-free operation are demonstrated for a 1.15-μm wavelength. In a push-pull mode of operation, the index in the guide and antiguide regions of the modulator change in opposing directions, which can be adjusted such that the resulting phase shift contributions to the guided mode cancel each other, resulting in zero net mode phase shift     

Power scaling of diode-pumped Nd:YVO/sub 4/ lasers

The evaluation of pump capability and scaling the output power of Nd:YVO/sub 4/ (vanadate) lasers are presented in this paper. Taking into account thermal fracture limitation and fundamental mode operation, systematic investigations of vanadate crystals have been conducted in an effort to scale the output power of diode-pumped lasers to higher levels. Based on the limitation of pump power, the input versus output power and beam propagation factor of vanadate lasers are optimized with knowledge of the thermal lensing effect and maximum pump power. The theoretical analyzes provide a good prediction for the output power of diode-pumped Nd:YVO/sub 4/ lasers, which is in agreement with the experiment. A practical example of a single-end-pumped vanadate laser is demonstrated with continuous-wave output powers of 9.8 W in the TEM/sub oo/ mode and 12.4 W in multimode.     

Modified suspended membrane photonic crystal D/sub 3/ laser cavity with improved sidemode suppression ratio

We have demonstrated the ability to selectively modify the mode structure of a multimoded photonic crystal laser cavity, based on the detailed knowledge of resonant modes in a suspended membrane D/sub 3/ microcavity. We have designed a microcavity in which the margins between the highest Q mode and the next highest Q modes have been increased. This modified cavity has been shown to have an improved sidemode suppression ratio under high power pumping condition.     

Continuous-wave operation of all-epitaxial InP-based 1.3 /spl mu/m VCSELs with 57% differential quantum efficiency

All-epitaxial InP-based 1.3 /spl mu/m VCSELs with a record-high continuous-wave differential quantum efficiency (57%) for single active region long-wavelength devices are demonstrated. Low-loss optical mode confinement is achieved through a selectively etched undercut tunnel-junction aperture. Singlemode continuous-wave lasing was observed up to 87/spl deg/C and the room-temperature output power was 1.1 mW at a current of 4.1 mA and a wavelength of 1.305 /spl mu/m.     

A dual-mode truly modular programmable fractional divider based on a 1/1.5 divider cell

A divide-by-1/1.5 divider cell using a dual edge-trigger technique is proposed. Based on this divider cell, a dual-mode programmable divide-by-X circuit is demonstrated in 0.18-/spl mu/m CMOS technology, where X=P or P.5 in one mode and 2P or 2P+1 in the other mode with P=128-255. When operated in the divide-by-2P/2P+1 mode, this circuit outputs a signal with 50% duty cycle. Theoretically, P can be any arbitrary and programmable integer.     

Polarization dependence of a 1.52 μm InGaAs/InP multiple quantumwell waveguide electroabsorption modulator

A ridge-waveguide In_0.53Ga_0.47As/InP multiple-quantum-well (MQW) electroabsorption modulator operating at a wavelength of 1.52 μm is demonstrated. The modulator exhibits large polarization-dependent electroabsorption behavior which favors the modulation of the TM mode. At a reverse bias of 10 V, the modulator has a 24.5-dB extinction ratio for the TM mode, whereas that for the TE mode is only 11.1 dB. Polarization-dependent saturation of absorption has been observed in this device for incident optical power levels of less than 1 mW     

Bidirectional Hybrid DWDM‐PON for HDTV/Gigabit Ethernet/CATV Applications

A new scheme for bi‐directional HDTV/Gigabit Ethernet/CATV transmission over a hybrid dense‐wavelength‐division‐multiplexing passive optical network (DWDM‐PON) is proposed and demonstrated. It is based on injection‐locked vertical‐cavity surface‐emitting lasers and distributed‐feedback laser diodes as transmitters. Services with 129 HDTV channels, a 1.25 Gbps Gigabit Ethernet connection, and 77 CATV channels are successfully demonstrated over 40 km single‐mode fiber links. Good performance of bit error rate, carrier‐to‐noise ratio, composite second order, and composite triple beat is achieved in our proposed bidirectional DWDM‐PON.     

Demonstration of 20 Gbit/s subcarrier multiplexed transmissionsystem

A 20 Gbit/s subcarrier multiplexed (SCM) optical transmission system is presented. To date, this represents the highest aggregate bit rate SCM transmission that has been demonstrated. Results show that the bit error rate (BER) is less than 10^-12 for a link loss of 29.5 dB, which corresponds to 118 km single mode fibre (SMF). Furthermore, excellent performance is demonstrated after transmission over 82 km of dispersion compensated SMF. Results suggest that the system can support transmission over multiple spans of optical fibre     

Low-chirp and high-power 1.55-/spl mu/m strained-quantum-well complex-coupled DFB laser

High-power, low-chirp, and low-threshold current characteristics of 1.55 /spl mu/m complex-coupled compressively strained InGaAsP quantum-well DFB laser with a loss grating are presented. Kink-free light-current characteristics with single-mode power over 40 mW are demonstrated for uncoated devices. A relatively low threshold current of 10 mA and a high slope efficiency of 0.23 W/A have been obtained even with the loss grating employed. Stable single-mode emission was demonstrated with a side mode suppression ratio up to 54 dB, a low chirp of less than 0.3 nm under 1 Gb/s pseudorandom digital modulation and a spectral linewidth of 8 MHz.     

Rational harmonic mode-locking of erbium-doped fiber laser at 40 GHz using a loss-modulated Fabry-Pe/spl acute/rot laser diode

Rational harmonic mode-locking of an Erbium-doped fiber ring laser (EDFL) at repetition frequency of 40 GHz is demonstrated by using a purely loss-modulated Fabry-Pe/spl acute/rot laser diode (FPLD) at 1 GHz. The FPLD is neither lasing nor gain-switching, which requires a threshold modulation power of 18 dBm to initiate harmonic mode-locking of the EDFL. After chirp compensation, the nearly transform-limited pulsewidth and spectral linewidth of 3 ps and 1.3 nm are obtained at repetition frequency of 40 GHz, which corresponds to a time-bandwidth product of 0.31. The EDFL gradually evolves from harmonic mode-locking to injection-locking mode as the FPLD changes from loss-modulation to gain-switching mode by increasing its dc driving current.