Thin Photo-Patterned Micropolarizer Array for CMOS Image Sensors

We fabricated and characterized a thin photo-patterned micropolarizer array for complementary metal–oxide–semiconductor (CMOS) image sensors. The proposed micropolarizer fabrication technology completely removes the need for complex selective etching. Instead, it uses the well-controlled process of ultraviolet photolithography to define micropolarizer orientation patterns on a spin-coated azo-dye-1 film. The patterned polymer film micropolarizer (10 $mu$m$times$10 $mu$m) exhibits submicron thickness (0.3 $mu$ m) and has an extinction ratio of ${sim}$100. Reported experimental results validate the concept of a thin, high spatial resolution, low-cost photo-patterned micropolarizer array for CMOS image sensors.      

Operation of a 25-Gb/s Direct Modulation Ridge Waveguide MQW-DFB Laser up to 85 $^{circ}$ C

We demonstrated a 25-Gb/s direct modulation up to 85 $^{circ}$C with a 1.3- $mu$m InGaAlAs ridge-waveguide multiple-quantum-well distributed-feedback laser. The dependence of the relaxation oscillation frequency on current was 3.3 GHz/mA$^{1 / 2}$, and this is the highest value ever reported for 200-$mu$m-long lasers in the 1.3-$mu$m wavelength region. The $alpha$ parameter was around 2.7 at 25 $^{circ}$C, and an error-free operation after a 10-km single-mode fiber transmission was obtained up to 85 $^{circ}$C.      

Elixir: High-Throughput Cost-Effective Dual-Field Processors and the Design Framework for Elliptic Curve Cryptography

We present a design framework that consists of a high-throughput, parallel, and scalable elliptic curve cryptographic (ECC) processor, and its cost-effectiveness methodology for the design exploration. A two-phase scheduling methodology is proposed to optimize the ECC arithmetic over both ${rm GF}(p)$ and ${rm GF}(2^m)$. Based on the methodology, a parallel and scalable ECC architecture is also proposed. Our dual-field ECC architecture supports arbitrary elliptic curves and arbitrary finite fields with different field sizes. The optimization to a variety of applications with different area/throughput requirements can be achieved rapidly and efficiently. Using 0.13-$mu$m CMOS technology, a 160-bit ECC processor core is implemented, which can perform elliptic-curve scalar multiplication in 340 $mu$s over ${rm GF}(p)$ and 155 $mu$s over ${rm GF}(2^m)$, respectively. The comparison of speed and area overhead among different ECC designs justifies the cost-effectiveness of the proposed ECC architecture with its design methodology.      

High-Power Large-Aperture Bottom-Emitting 980-nm VCSELs With Integrated GaAs Microlens

Microlens-integrated bottom-emitting 980-nm vertical-cavity surface-emitting lasers (VCSELs) with an emitting window aperture of 400 $mu$m have been fabricated. A novel material structure with nine InGaAs–GaAsP quantum wells and slightly decreased reflectivity of n-type distributed Bragg reflectors (n-DBRs) are employed to increase the output power. A convex microlens is fabricated by a one-step diffusion-limited wet-etching technique on the GaAs substrate. The diameter of the active layer is about 200 $mu$m after lateral oxidation, and the nominal diameter of the microlens is 400 $mu$m. The maximum output power is 200 mW at continuous-wave operation at room temperature. The far-field divergence angles $theta_{parallel}$ and $theta_{bot}$ of the single device at a current of 4A are 8.7 $^{circ}$ and 8.4 $^{circ}$, respectively. The optical beam performance between the microlens-integrated VCSEL and ordinary VCSEL is compared.      

High-Speed Metal–Germanium–Metal Configured PIN-Like Ge-Photodetector Under Photovoltaic Mode and With Dopant-Segregated Schottky-Contact Engineering

In this letter, we present a high-speed metal– germanium–metal configured Ge-photodetectors (MGM-PDs) under photovoltaic mode (i.e., 0-V operation). The metal contacts are engineered by an asymmetrical (i.e., boron and arsenic) dopant-segregation scheme on Schottky-contacts to suppress the dark current, and are with scaled spacing ( $sim$0.8 $mu$m). The MGM-PD (with $sim$300-nm-thick Ge) is integrated on a silicon-on-isolator waveguide with complementary metal–oxide–semiconductor field effect transistor compatible process. For $lambda =1550$ nm, under 0-V bias, the devices illustrate a reasonable responsivity $sim$0.17 A/W and a fast pulse response of 18 ps.      

A 36–80 GHz High Gain Millimeter-Wave Double-Balanced Active Frequency Doubler in SiGe BiCMOS

This letter presents a high conversion gain double-balanced active frequency doubler operating from 36 to 80 GHz. The circuit was fabricated in a 200 GHz ${rm f}_{rm T}$ and ${rm f}_{max}$ 0.18 $mu$m SiGe BiCMOS process. The frequency doubler achieves a peak conversion gain of 10.2 dB at 66 GHz. The maximum output power is 1.7 dBm at 66 GHz and ${-}3.9$ dBm at 80 GHz. The maximum fundamental suppression of 36 dB is observed at 60 GHz and is better than 20 dB from 36 to 80 GHz. The frequency doubler draws 41.6 mA from a nominal 3.3 V supply. The chip area of the active frequency doubler is 640 $mu$m $,times,$424 $mu$m (0.272 mm $^{2}$) including the pads. To the best of authors' knowledge, this active frequency doubler has demonstrated the highest operating frequency with highest conversion gain and output power among all other silicon-based active frequency doublers reported to date.      

Compact Microracetrack Resonator Devices Based on Small SU-8 Polymer Strip Waveguides

Compact microracetrack resonator (MRR) devices are presented with small SU-8 polymer strip waveguides. The SU-8 strip waveguide has an SU-8 polymer core $(n {sim} 1.573)$ , a SiO$_{2}$ buffer $(n {sim} 1.445)$, and an air cladding. The fabricated straight waveguide has a low propagation loss of about 0.1 dB/mm. With such a high index-contrast optical waveguide, a compact MRR with a small bending radius ( $sim$150 $mu$m) are designed and fabricated. The measured spectral responses of the through/drop ports show a $Q$-factor of 8000.      

Fabrication and Characterization of Fused Microfiber Resonators

We fabricate a 2.6-mm-diameter loop resonator from a tapered, step-index silica fiber of thickness $sim$ 7.2 $mu$ m. The resonator has a coupling region that is fused with a CO$_{2}$ laser for reducing structural instabilities and improving the overall stability of the device. We experimentally demonstrate optical resonances with a $Q$-factor ${ge}$25 000 at a free-spectral range of 0.19 nm.      

A 300 nW, 15 ppm/$^{circ}$C, 20 ppm/V CMOS Voltage Reference Circuit Consisting of Subthreshold MOSFETs

A low-power CMOS voltage reference was developed using a 0.35 $mu$m standard CMOS process technology. The device consists of MOSFET circuits operated in the subthreshold region and uses no resistors. It generates two voltages having opposite temperature coefficients and adds them to produce an output voltage with a near-zero temperature coefficient. The resulting voltage is equal to the extrapolated threshold voltage of a MOSFET at absolute zero temperature, which was about 745$~$mV for the MOSFETs we used. The temperature coefficient of the voltage was 7 ppm/ $^{circ}$C at best and 15 ppm/$^{circ}$C on average, in a range from ${-}$ 20 to 80$^{circ}$ C. The line sensitivity was 20 ppm/V in a supply voltage range of 1.4–3 V, and the power supply rejection ratio (PSRR) was ${-}$45 dB at 100 Hz. The power dissipation was 0.3 $mu$W at 80$^{circ}$C. The chip area was 0.05 mm$^2$ . Our device would be suitable for use in subthreshold-operated, power-aware LSIs.      

Conductively Cooled 637-nm InGaP Broad-Area Lasers and Laser Bars With Conversion Efficiencies Up to 37% and a Small Vertical Far Field of 30$^{circ}$

Highly efficient operation of 637-nm broad-area (BA) laser diodes and laser bars with a small vertical far field of 30$^{circ}$ (full-width at half-maximum) is reported. The laser structure consists of an InGaP quantum well embedded in AlGaInP waveguide layers and n-AlInP and p-AlGaAs cladding layers. Single BA emitters with a stripe width of 30 $mu$m emitted a maximum continuous-wave (CW) power of 540 mW at 15 $^{circ}$ C. Six-millimeter-wide laser bars with 12 30- $mu$m-wide emitters (filling factor of 6%) reached CW power levels of 5.4 W at 15 $^{circ}$C. The maximum conversion efficiency of single lasers and laser bars at 15 $^{circ}$ C was 37% and 31%, respectively.      

A Low-Voltage Processor for Sensing Applications With Picowatt Standby Mode

Recent progress in ultra-low-power circuit design is creating new opportunities for cubic millimeter computing. Robust low-voltage operation has reduced active mode power consumption considerably, but standby mode power consumption has received relatively little attention from low-voltage designers. In this work, we describe a low-voltage processor called the Phoenix Processor that has been designed at the device, circuit, and architecture levels to minimize standby power. A test chip has been implemented in a carefully selected 0.18 $mu$m process in an area of only 915$, times ,$915 $mu$ m$^{2}$ . Measurements show that Phoenix consumes 35.4 $~$pW in standby mode and 226 nW in active mode.      

Line-Tunable Singly Resonant Optical Parametric Oscillator in Mid-Infrared Spectral Range Based on KTA Crystal

Line-tunable narrow-linewidth mid-infrared radiation in 3–5-$mu$m spectral range by singly resonant optical parametric oscillation technique based on a KTA crystal pumped by 1.064-$mu$ m radiation from a $Q$ -switched Nd:YAG laser using different gratings has been demonstrated. Thresholds of oscillation energy at different cavity lengths and at different idler wavelengths with different gratings have been measured. Energy of the generated radiation at 3.6 $mu$ m as a function of pump beam energy at different cavity lengths with different gratings have been measured. Maximum energy obtained at 3.6-$mu$m radiation with a grating having grooves density 85 l/mm at 55-mm cavity length is 4.6 mJ when the cavity was pumped by 42.6-mJ energy, which corresponds to conversion efficiency from pump beam energy to generated idler beam energy 10.8% and maximum slope efficiency achieved was 23.6%. The linewidth obtained with a grating having grooves density 600 l/mm at 3.7 $mu$m was 0.53 cm $^{- 1}$.      

Injection Locking and Switching Operations of a Novel Retro-Reflector-Cavity-Based Semiconductor Micro-Ring Laser

Injection locking and switching characteristics are investigated in the novel retro-reflector-cavitiy-based semiconductor ring laser with equivalent circular radius of 26 $mu$ m. The allowed detuning range is up to ${sim}$3 GHz wide and the highest side mode suppression ratio of ${sim}$ 43.7 dB can be achieved. A fast response speed of ${sim}$70 ps to the cavity is achieved, which indicates that this device can be utilized as an all optical switch at a data rate of 10 Gb/s or higher.      

VCSEL Module With Polymer Optical Output Rods to Enable High Efficiency Coupling for Optical Interconnection

New vertical-cavity surface-emitting laser (VCSEL) modules—designed with a optical output rod surrounded by cladding—have been proposed to realize high-efficiency low-cost optical interconnection. Prototypes have been fabricated using a photomask transfer method employing two kinds of ultraviolet curable resin. Observation of the near-field pattern and eye pattern for signal transmission shows that output rods with a diameter of 50- $mu$m efficiently confine the laser beam as an optical waveguide. In addition, ray tracing simulation indicates that this new VCSEL offers greater positional tolerance—as much as $+$18/ $-$22 $mu$m—for coupling to optical wiring in 90$^{circ}$ light path conversion.      

Q-Band pHEMT and mHEMT Subharmonic Gilbert Upconversion Mixers

This letter makes a comparison between Q-band 0.15 $mu{rm m}$ pseudomorphic high electron mobility transistor (pHEMT) and metamorphic high electron mobility transistor (mHEMT) stacked-LO subharmonic upconversion mixers in terms of gain, isolation and linearity. In general, a 0.15 $mu{rm m}$ mHEMT device has a higher transconductance and cutoff frequency than a 0.15 $mu{rm m}$ pHEMT does. Thus, the conversion gain of the mHEMT is higher than that of the pHEMT in the active Gilbert mixer design. The Q-band stacked-LO subharmonic upconversion mixers using the pHEMT and mHEMT technologies have conversion gain of $-$7.1 dB and $-$0.2 dB, respectively. The pHEMT upconversion mixer has an ${rm OIP}_{3}$ of $-$12 dBm and an ${rm OP}_{1 {rm dB}}$ of $-$24 dBm, while the mHEMT one shows a 4 dB improvement on linearity for the difference between the ${rm OIP}_{3}$ and ${rm OP}_{1 {rm dB}}$. Both the chip sizes are the same at 1.3 mm $times$ 0.9 mm.      

Ultrashort Polarization Splitter Using Two-Mode Interference in Silicon Photonic Wires

An ultrashort polarization splitter based on the zero-gap directional coupler is proposed and realized. Its interference section is 8.8 $mu$m long. It is also shown that the length of the interference section can be reduced to about 2.1 $mu$m. The crosstalk for both transverse-electric (TE) and transverse-magnetic (TM) polarizations is 16 dB at a wavelength of 1.55 $mu$m. The extinction ratios of TE and TM polarizations are 18.2 and 13.7 dB, respectively. The device has 3-dB bandwidth of 43 nm in TE polarization and 50 nm in TM polarization with the center wavelength at 1.55 $mu$ m.      

Injection-Type GaInAsP–InP–Si Distributed-Feedback Laser Directly Bonded on Silicon-on-Insulator Substrate

An injection-type distributed-feedback laser, with wirelike active regions, directly bonded on a silicon-on-insulator substrate, was realized. A low threshold current $I _{rm th}$ of 104 mA was obtained at a stripe width of 25 $mu$m and a cavity length of 1 mm. A sidemode suppression ratio of 28 dB was obtained at $1.3 I _{rm th}$.      

Thick Absorption Layer Uni-Traveling-Carrier Photodiodes With High Responsivity, High Speed, and High Saturation Power

High responsivity backside-illuminated uni-traveling-carrier photodiodes (PDs) with a 1.2-$mu$ m-thick p-doped absorption layer are demonstrated. The fabricated PDs achieve simultaneously high speed, high responsivity, and good linearity under high-power operation. The measured responsivity at 1.55 $mu$m is larger than 0.83 A/W at low photocurrent and increases up to 1 A/W at 75 mA. The measured bandwidth increases from 9 GHz at 1 mA up to 24 and 29 GHz at 50 mA, for 25- and 20-$mu$m-diameter PDs, respectively. Good linearity is demonstrated with a third-order intercept point of 30 dBm at 10 GHz and 50 mA.      

Twin-Contact 645-nm Tapered Laser With 500-mW Output Power

High brightness tapered lasers emitting around 650 nm were developed. We realized 2-mm-long devices with 750- $mu$m straight section, 1250-$mu$m tapered section, and 4$^{circ}$ taper angle. The input currents into both sections were independently controlled. The laser reached 500-mW output power in continuous-wave operation in a nearly diffraction-limited beam quality. A modulation efficiency of 7.5 W/A was achieved.      

Chalcogenide As$_{2}$S$_{3}$ Suspended Core Fiber for Mid-IR Wavelength Conversion Based on Degenerate Four-Wave Mixing

A chalcogenide optical fiber of special design is proposed to convert a short-wavelength infrared radiation (around 2 $mu$m) up to a second transparency window of atmospheric air (around 4.5 $mu$ m) by degenerate four-wave mixing. The fiber supports a small core surrounded by three large air holes. The zero-dispersion wavelength is shifted down to 2 $mu$m in this fiber by properly tailoring the fiber core. We demonstrate by solving the nonlinear SchrÖdinger equation that efficient wavelength-conversion can be obtained by pumping the fiber with a Tm : SiO$_{2}$ pulsed fiber laser.