Very simple approach for high performance DFBlaser-electroabsorption modulator monolithic integration

A novel and very simple approach is demonstrated for distributed feedback laser-electroabsorption modulator monolithic integration. This uses the same strained multiquantum well active layer for both optical functions. Very high performance (13.6 dB extinction ratio at 1.5 V operating voltage for a 70 μm long modulator) is reported at 1.5 μm     

Optical full-duplex transmission with diode laser amplifiers

Error-free, simultaneous bidirectional optical transmission at 50 Mb/s over 5.5 km of fiber using only a single antireflection coated Fabry-Perot laser transmitter/detector at each end is demonstrated. A baseband digital signal is transmitted in one direction, while a digitally modulated subcarrier signal is transmitted in the opposite direction. At the 1.5-μm operating wavelength, the system length is dispersion limited due to the wide spectral widths of the signals. Therefore, it is expected that a system operating at the 1.3-μm low-dispersion window will show an improved capacity. The additional device capability of optical gain makes this scheme attractive in multiport-full-duplex applications     

1.5-μm-band optical time domain reflectometer for single-modeoptical fiber using a P2O5-highly-doped fiberRaman laser

A wide-dynamic-range 1.5-μm-band optical time-domain reflectometer (OTDR) for single-mode optical fibers using a P₂O₅-highly-doped fiber Raman laser light source and a cooled Ge-p-i-n photodiode is realized for the first time. The stimulated-Raman-scattering properties of P₂O₅-doped single-mode fiber are investigated. Using this fiber and an Nd:YAG laser operating at 1.32 μm, a high-power light pulse at 1.59 μm is generated with high efficiency. Using the stimulated-Raman-scattering light as the light source and a high-sensitivity optical receiver, a 1.5-μm-band OTDR having a one-way dynamic range of 35 dB is realized     

The effect of spurious intensity modulation in semiconductor diode lasers on the performance of optical heterodyne frequency shift-keyed communications systems

Analytical expressions are derived for the bit-error rate (BER) of anM-ary frequency shift-keyed (FSK), heterodyne, optical communication system with noncoherent demodulation in the presence of spurious intensity modulation (SIM) and frequency noise. The SIM degradation of an FSK system, implemented with semiconductor diode lasers, is estimated for lasers with zero and nonzero linewidths and will be discussed for a distributed feedback laser operating at 1.5μm and a channeled substrate planer laser operating at 0.83 μm. The SIM power penalty is typically less than 1 dB, but can exceed 1 dB for 2-, 4-, and 8-ary FSK at data rates above 1 Gbit/s.     

1.3 ?m/1.5 ?m bidirectional WDM optical-fibre transmission system experiment at 144 Mbit/s

Results are reported of a 1.3 ?m/1.5 ?m bidirectional WDM transmission system experiment operating at 144 Mbit/s over 58 km of cabled single-mode fibre. Regenerators used Bell Laboratories-developed 1.3 and 1.5 ?m InGaAsP semiconductor lasers, InGaAs PIN diodes, microwave monolithic amplifiers and optical bidirectional couplers.     

Megahertz linewidth from a 1.5 ?m semiconductor laser with HeNe laser injection

The linewidth of a 1.5 ?m semiconductor laser has been reduced from > 1 GHz to < 1.5 MHz by injection locking the laser to the low-power narrow-linewidth output from an HeNe laser operating at 1.523 ?m. A collimated-beam power of 750 ?W was obtained in the injection-locked semiconductor laser mode.     

A new lensed-fiber configuration employing cascaded GI-fiber chips

A new scheme is proposed for lensed fibers having high coupling efficiency between laser diodes and single-mode fibers with a long working distance. The new lensed fiber consists of a pair of GI-fiber tips having different focusing parameters. The measured net coupling loss between a laser diode operating at a wavelength of 1.3 μm and a single-mode fiber is as low as 1.5 dB. The working distances are around 50 μm, much longer than those of conventional lensed fibers     

Analysis of the sign reversal of the photodetected signal responsein a multielectrode semiconductor optical amplifier

We present a theoretical analysis and experimental results for a two-electrode (200 μm×300 μm) 1.5-μm semiconductor optical amplifier (SOA) used in photodetection. The experimental results show that at a particular operating point regarding current and optical input power, a sign reversal of the photodetected signal response, and a frequency bandwidth shape modification are obtained at the SOA front contact. These results are confirmed by simulation and explained by the developed theoretical photodetection expression obtained by small signal analysis from the rate equation     

Increased attenuation in optical fibres caused by diffusion of molecular hydrogen at room temperature

A new set of absorption peaks has been observed at wave-lengths between 1.5 and 2.5 ?m in silica-based optical fibres which have been exposed to hydrogen at room temperature. The largest peak, at 2.42 ?m, is identified as being due to the fundamental molecular hydrogen vibrational absorption. Other peaks in the set are related to the fundamental with the same energy shifts as previously reported for the first overtone spectrum. The implications of both sets of peaks are quantified for the operating windows of optical fibre systems at 1.3 and 1.55 ?m.     

Single and multimode fiber bandwidth measurements with single and multilongitudinal mode lasers operating at 0.8-, 1.3-, and 1.5-µm wavelength

The bandwidth characteristics of single and multimode optical fibers have been investigated with single and multilongitudinal mode laser sources operating at 0.8, 1.3, and 1.5 μm. It is shown that single-mode fiber with a cutoff wavelength of 1.3 μm can support 1 Gb/s transmission over at least 7.5 km with a 0.8-μm laser source.     

Er3+-Yb3+ and Er3+ doped fiberlasers

Single-mode fiber lasers operating at ~1.57 μm are described. Output powers of >2 mW are reported for laser diode pumped operation. Direct comparison is made between fiber lasers using sensitized erbium (Er³⁺ and Yb³⁺) and erbium on its own. The performance of Er³⁺-Yb³⁺ fiber lasers is analyzed in more detail as a function of fiber length. Both CW and Q-switched operations are studied and the results obtained demonstrate that practical sources at 1.5 μm are available from diode pumped Er³⁺ -Yb³⁺ systems     

Spectral properties of strongly coupled 1.5 µm DFB laser diodes

Spectral measurements of strongly coupled DFB lasers operating at 1.5 μm are presented. The magnitude of the coupling coefficientkin these devices was determined to be 80 cm^-1for lasers withlambda = 1.12 mum cladding layers and 160 cm^-1for devices withlambda = 1.3 mum cladding layers. These values forkare believed to be the largest reported for 1.5 μm DFB lasers. CW spectral linewidths as low as 10 MHz at 15 mW output power were obtained, and the linewidth was observed to vary approximately as the inverse of the device length cubed. Spectral measurements performed under 2 Gbit/s direct modulation exhibited a side mode suppression ratio of >38 dB. The effects of transient wavelength chirping were also investigated in detail and the maximum wavelength deviation was found to be ≃1.5 Å.     

Generation of high-power femtosecond pulses near 1.5 μm using acolor-center laser system

The authors have developed a high-power F-center laser system capable of generating femtosecond pulses with energies exceeding 50 pJ at wavelengths near 1.5 μm. Short pulses (140 fs) from an additive-pulse mode-locked NaCl laser are amplified in a multipass NaCl amplifier at kilohertz repetition rates. The system can generate peak powers approaching 500 MW, with wavelengths tunable from 1.52 to 1.64 μm. The amplified pulses are used to generate a continuum in various solid media without optical damage. The continuum generated in BaF₂ is extremely broad, extending from below 400 nm to 3.5 μm. Construction and operating details are discussed as well as the system's utility for femtosecond measurements in the infrared and high-power experiments     

Cell-plate line connecting complementary bit-line (C3)architecture for battery-operated DRAMs

In low-voltage operating DRAMs, one of the most serious problems is how to maintain sufficient charge stored in the memory cell, which is concerned with the operating margin and soft error immunity. An array architecture called the cell-plate line connecting complementary bit-line (C³) architecture, which realizes a large signal voltage on the bit-line pair and low soft error rate (SER) without degrading the reliability of the memory cell capacitor dielectric film, is proposed. This architecture requires no unique process technology and no additional chip area. With the test device using the 16-Mb DRAM process, a 130-mV signal voltage is observed at 1.5-V power supply with 1.6-μm×3.2-μm cell size. This architecture should open the path for the future battery-backup and/or battery-operated high-density DRAMs     

Distributed-feedback quantum cascade lasers emitting in the 9-μmband with InP top cladding layers

Two different high performance quantum cascade distributed-feedback lasers with four quantum-well-based active regions and InP top cladding layers are presented. The first device, which emitted at 9.5 μm, was mounted junction down in order to get high average powers of up to 71 mW at -30°C and 30 mW at room temperature. The other device, which lased at 9.1 μm, was optimized for high pulsed operating temperatures and tested up to 150°C at 1.5% duty cycle. The emission of both lasers stayed single mode with more than 20-dB side-mode suppression ratio over the entire investigated power and temperature range     

Optimized design and fabrication of high-speed and high-radiance InGaAsP/InP DH LED in the 1-µm wavelength region

Design and fabrication of an InGaAsP/InP double-heterostructure (DH) light-emitting diode (LED) with a monolithic lens, Which exhibits high-speed and high-radiance performance, have been presented. Dependences of operating characteristics such as the coupled power, the current-light linearity and the cutoff frequency on the LED, and the fiber structural parameters, have been analyzed, modeled, and applied to complete an optimal design. It has been found that a high magnification lens allows one to maximize both the coupled output power and the response speed. LED'S coupled to 50-µm core 0.2-NA graded-index fiber have been fabricated at the wavelengths of 1.15, 1.3, and 1.5 µm. A significant improvement has been achieved particularly in the cutoff frequency, and the maximum value of 120 MHz at the current of 100 mA has been realized at 1.3-µm wavelength without reduction of the coupled power (35 µW). High-speed and high-power performances of these diodes are promising for their application to high bit-rate transmission systems.     

Design of double and triple quantum wells for InGaAs-AlAsSbintersubband unipolar semiconductor lasers

InGaAs-AlAsSb double and triple quantum well (QW) structures were designed in an effort to shorten the wavelength to less than 2 μm for possible application to intersubband unipolar lasers. Wavelengths corresponding to the intersubband separation, the minimum and maximum operating electric field, optical-phonon-limited nonradiative scattering time, and escape time from the QW were simulated. It was found that suitable nonradiative transition times can be obtained by properly designing the coupling layer thickness for both kinds of QW's. The minimum wavelength is 1.5 μm and an operating electric field is above 130 kV/cm for wavelengths <2 μm in the double QW. On the other hand, the minimum operating electric field is less than 10 kV/cm and the minimum wavelength is about 1.7 μm for the triple QW. The triple QW is suitable for an electric-field induced wavelength tunable laser     

High contrast GaInAs:Fe photoconductive optical AND gate fortime-division demultiplexing

A high-contrast, three port optical AND gate based on the photoconductive effect in Ga_0.47In_0.53As:Fe and operating in the λ=1.3-5 μm wavelength range is demonstrated. A 250:1 optical power contrast ratio (or 48 dB in electrical power after detection) is obtained in an optical-to-optical time division demultiplexing of a 100 MHz pulse train by a 6.25 MHz clock, both at λ=1.3 μm, with the demultiplexed output pulses at λ=1.5 μm     

Design optimization for efficient erbium-doped fiber amplifiers

The gain and pumping efficiency of aluminosilicate erbium-doped fiber amplifiers (EDFAs) are analyzed as a function of guiding parameters and Er-doping profile for two pump wavelengths of λ _p=980 nm and λ_p=1.47 μm. Three designs of fiber-amplifier waveguides are considered: one with the same mode size as standard 1.5-μm communication fibers (type 1); one with the same mode size as standard 1.5-μm dispersion-shifted fibers (type 2); and one with mode size smaller than those of communication fibers (type 3). For the 1.47-μm pump, fundamental LP₀₁ mode excitation is assumed, while for the λ_p=980-nm pump, concurrent excitation of LP₁₁ modes is considered. It is shown that excitation of higher-order pump modes at 980 nm does not significantly affect the amplifier gain performance. The effect of concentrating the Er³⁺ doping near the center of the fiber core is shown to increase the amplifier gain coefficients by a factor of 1.5 to 2     

On the SiO2-based gate-dielectric scaling limit forlow-standby power applications in the context of a 0.13 μm CMOS logictechnology

This paper describes a leading-edge 0.13 μm low-leakage CMOS logic technology. To achieve competitive off-state leakage current (I _off) and gate delay (T_d) performance at operating voltages (V_cc) of 1.5 V and 1.2 V, devices with 0.11 μm nominal gate length (L_g-nom) and various gate-oxide thicknesses (T_ox) were fabricated and studied. The results show that low power and memory applications are limited to oxides not thinner than 21.4 Å in order to keep acceptable off-state power consumption at V_cc=1.2 V. Specifically, two different device designs are introduced here. One design named LP (T_ox=26 Å) is targeted for V_cc=1.5 V with worst case I_off <10 pA/μm and nominal gate delay 24 ps/gate. Another design, named LP1 (T_ox=22 Å) is targeted for V_cc =1.2 V with worst case I_off<20 pA/μm and nominal gate delay 27 ps/gate. This work demonstrates n/pMOSFETs with excellent 520/210 and 390/160 μA/μm nominal drive currents at V_cc for LP and LP1, respectively. Process capability for low-power applications is demonstrated using a CMOS 6T-SRAM with 2.43 μm² cell size. In addition, intrinsic gate-oxide TDDB tests of LP1 (T _ox=22 Å) demonstrate that gate oxide reliability far exceeding 10 years is achieved for both n/pMOSFETs at T=125°C and V _cc=1.5 V