Temperature Dependence Of Gain Research Articles

Dynamical Hysteresis and Thermal Effects in Vertical-Cavity Surface-Emitting Lasers

We study numerically the polarization-resolved light-output characteristic of vertical-cavity surface-emitting lasers (VCSELs) using the spin-flip model for VCSELs extended to take into account thermal effects via a dynamical equation for the active region temperature, including heat dissipation, heating due to nonradiative carrier recombination, and Joule effect. The temperature dynamics is coupled to the carrier and optical field dynamics via a frequency and temperature-dependent gain coefficient. We show that the interplay of thermal effects and injection current variation can result in turn-on and turn-off hysteresis cycles that can be, depending on various model parameters, positive or negative. In the first case, the turn-on occurs at a higher value of the bias current than the turn-off; in a negative hysteresis cycle, the laser turns-on at a lower value of the bias current than the turn-off. These results are interpreted in terms of the interplay of the two time-scales determined by the injection current swept rate and the thermal relaxation rate.

12-bit accurate voltage-sensing ADC with curvature-corrected dynamic reference

A sigma-delta analogue-to-digital converter (ADC) with a dynamic voltage reference is presented that achieves 12-bit absolute accuracy over the extended industrial temperature range (-40 to 105°C). Temperature-dependent gain errors due to the reference's curvature are digitally corrected by adjusting the gain of the ADC's decimation filter. The required correction factor is obtained by first using the reference to make a temperature measurement, and then translating the result into a correction factor by means of a lookup table and a linear interpolator. Thus, a dynamic voltage reference is realised with a measured temperature drift of less than 1.7 ppm/°C. The ADC was fabricated in 0.7 ?m CMOS technology and consumes 85 ?A from a 2.5-5.5 V supply.

Temperature dependent gain characteristics in GaN-based vertical-cavity surface-emitting lasers

Temperature dependent gain characteristics and linewidth enhancement factor (alpha-factor) of vertical-cavity surface-emitting lasers with InGaN/GaN multiple quantum wells were studied by measuring the photoluminescence spectra below the threshold condition and analyzed by using the Hakki-Paoli method. The optical gain and differential gain showed a more rapid increase as a function of the injected carriers as temperature decreased. The alpha-factor for the lasing mode was estimated as 2.8 at room temperature and decreased to a value as low as 0.6 at 80 K.

Monte-Carlo-based spectral gain analysis for terahertz quantum cascade lasers

Employing an ensemble Monte Carlo transport simulation, we self-consistently analyze the spectral gain for different terahertz quantum cascade laser structures, considering bound-to-continuum as well as resonant phonon depopulation designs. In this context, we investigate temperature dependent gain broadening, affecting the temperature performance of terahertz structures. Furthermore, we discuss the influence of the individual scattering mechanisms, such as electron-electron, impurity and interface roughness scattering. A comparison of the simulation results to experimental data yields good agreement.

On the Temperature-Dependent Gain and Noise Figure Analysis of C-Band High-Concentration EDFAs With the Effect of Cooperative Upconversion

We present an efficient temperature-dependent analysis to study the effect of cooperative upconversion on the temperature-dependent gain (TDG) performance of the C-band erbium-doped fiber amplifier (EDFA) at high-concentration. The influence of cooperative upconversion on the TDG is examined by using a set of temperature-dependent rate and light propagation equations. In the analysis given, the amplified spontaneous emission (ASE), as well as the excited state absorption (ESA) are also considered. In the forward pumping configuration at a signal wavelength of 1547 nm and in the temperature range of - 40degC to + 80degC, the variations of the TDG and the noise figure (NF) are about 1.7 and 0.9 dB, respectively. Numerical analysis results show that, with 260-mW/1480-nm pump power, an erbium-doped fiber amplifier having a doping concentration of 4.4 times 1026 ion/m3 and optimum length of 9.2 cm may reach a signal gain of 44.6 dB and a noise figure of 3.9 dB at room temperature.

Temperature performance of terahertz quantum-cascade lasers: experiment versus simulation

We report the electrical and the optical characteristics of 2 THz quantum-cascade lasers with a similar four-well resonant-phonon design. A Monte Carlo simulation, employed to evaluate the temperature performance of the device, indicates that the degradation of material gain with increasing temperature is attributed to the rapid decrease in the lifetime of the upper lasing level and the relatively stable lifetime of the lower lasing level. Because of the broadening effect of the temperature dependent gain profile, our calculations overestimate the peak gain and subsequently overrate the maximum operating temperature. Under a linear approximation condition, the deduced maximum operating temperature is in good agreement with experiment. Both experiment and simulation show that the lasing frequency is insensitive to temperature.

An improved transmission line laser model for multimode laser diodes incorporating thermal effects

An improved transmission line model to study the thermal effects in semiconductor laser diodes is reported in this paper. The temperature effects in the laser characteristics are obtained by incorporating temperature dependent gain and carrier density equations for the laser cavity. These primary factors are introduced in the regular transmission line laser model to estimate the static and dynamic characteristics of an 1.3μm InGaAsP double heterostructure laser diode. The results show good agreement with the experimental observation and solution of rate equations referred in the literature. The key feature of this model is that it provides the laser spectra at various temperatures. Based on the model, time dependent evolution of optical spectrum, temperature dependent optical output and frequency chirp are evaluated. Further the distribution of photon and electron density within the cavity is also determined.

Effect of Printed Circuit Board Structures on Temperature-Dependent Gain Characteristics of RF Power Amplifier Chips

We fabricated and characterized heterojunction field effect transistor radio frequency (RF) power amplifier (PA) test fixtures, for wireless applications, with various printed circuit board (PCB) structures. The RF matching and bias circuits of the test fixtures were designed so that they had the same RF characteristics. The only source of the variation of the RF gain (S21) was different thermal characteristics of each PCB. The values of the junction temperature (TJ) and the junction-to-ambient thermal resistance (R J A) of each test fixture were shown to be changed as much as 80deg C and 30deg C / W, respectively, by the change of PCB structures. The change of Rja was shown to be originated from the change of the PCB thermal resistance, assuring that the structure of the PCB was the dominant factor in determining R J A Finally, we obtained a universal relation between S21 of the amplifier and Tj. This work suggests that thermal budget of PCB is as important as that of package in wireless RF equipments.

Midwavelength Infrared Avalanche Photodiode Using InAs–GaSb Strain Layer Superlattice

InAs-GaSb strain layer superlattice p+-n--n avalanche photodiodes (APDs) are fabricated using a newly introduced electron-beam aided zinc sulfide deposition. Temperature-dependent measurements were performed on 300 times 300 mum2 mesa etched APDs. The effect of passivation was also studied on the diode characteristics and APD performances. Temperature-dependent gain strongly correlates with avalanche mechanism.

The temperature dependency of EDFAs in the 1480 nm pumping configuration

A theoretical study of the temperature-dependent gain and noise figure effects on erbium-doped fiber amplifiers (EDFAs) pumped at 1480nm is investigated, solving the propagation equations related to two level systems. The solution of these equations is based on the population and temperature difference among amplification levels. The temperature-dependent propagation equation considered is used to determine the gain and noise figure effects on EDFAs. The population difference depends on pump and signal powers, Boltzmann factor KB, cross-sections, noise figure (NF) and Er3+ concentration. The temperature-dependent gain and noise figure effect the EDFA length are numerically obtained for the temperature range of −20°C to +60°C. All of the analyses consist of the amplified spontaneous emission (ASE) effect.

Temperature-Dependent Gain and Threshold in P-Doped Quantum Dot Lasers

The role of changes in gain and nonradiative recombination as a function of temperature in p-doped quantum dot samples that exhibit a minimum in the threshold current versus temperature characteristics are examined using a detailed analysis based on the multisection measurement method. An injection level is defined as the difference between the transparency energy and the transition energy of the dot states so that the results at different temperatures may be compared. The temperature dependence of the injection level necessary to achieve the required gain produces the initial decrease in nonradiative recombination current and threshold current between 250-280 K. At higher temperatures, the nonradiative recombination increases due to both an increase in the injection level required to achieve a fixed value of gain and because of an increase in the nonradiative recombination at fixed injection level. Using measurements of the population inversion function it is shown that the reduction in the injection level required to achieve a fixed value of gain between 250-280 K is caused by the thermalization of the carrier distribution over this temperature range. Subsequent increases in the injection level required to achieve a fixed value of gain are due to the increasing thermal distribution of carriers over the available states at higher temperatures.

Temperature-Dependent Gain Variation Reduction in$C$-Band Erbium-Doped Fiber Amplifier Using Phosphorus-Erbium-Doped Silica Fiber

We propose a new technique to reduce the temperature-dependent gain (TDG) tilt of erbium-doped fiber amplifier in the C-band by supplying a composite optical gain block, conventional aluminum-rich erbium-doped fiber (EDF) serially concatenated with a special EDF composed of phosphorus-doped silica host, which showed opposite TDG coefficients in the C-band. The TDG variation was suppressed to less than plusmn0.45 dB for the saturated gain of 16 dB in 1525-1565 nm, within the temperature range of -40degC to +80 degC

Analysis of temperature-dependent optical gain in GaN-InGaN quantum-well structures

The temperature dependent spectral gain in InGaN-GaN multiple quantum-well structures with 10% In content is investigated. Mode gain is measured in a temperature range between 239 K and 312 K using the Hakki-Paoli technique and compared to simulations. The simulation accounts for temperature-dependent polarization dephasing, and hence homogeneous broadening, in a rigorous fashion, without any fit parameter. It is found that the evolution of the gain spectrum with temperature at different drive currents can be modeled using a temperature-independent single value for inhomogeneous broadening. The resulting compositional fluctuations are compared to structural measurements

Low Noise-figure Miniature Erbium-doped Fibre Amplifier using Uncooled Pump Laser

A miniature-size erbium doped fibre amplifier (MS-EDFA) is constructed with a saturation power of 17.0 dBm and low noise figure of 5.2 dB using an uncooled pump laser. The MS-EDFA has achieved low polarization dependent gain, large signal gain and small signal gain of 0.05 dB, 15 dB (at Pin = +2 dBm) and 42 dB (at Pin = −30 dBm), respectively, with negligible temperature dependent gain. The dimension of MS-EDFA is only twice than a typical credit card.

Stabilizing scintillation detector systems by exploiting the temperature dependence of the light pulse decay time

Scintillation detectors must tolerate a wide range of ambient temperatures and strong temperature slopes when used in outdoor applications. Such demanding conditions are typical for all homeland security applications. An effective and efficient detector stabilization compensating for temperature dependent gain shifts is essential to maintain energy calibration and resolution. Reliable, well-established solutions are based on radioactive reference sources; however, alternatives are much asked for. The gain shift correction for the temperature dependence of the scintillation light output requires elaborate hardware and software means without a reference source. Strong and rapid temperature changes further complicate the situation as there is no thermal equilibrium in the detector but rather a temperature field. This paper presents a new technique of gain stabilization which considers the effective scintillator temperature by analyzing the average pulse shape of detector signals. The pulse shape is correlated with the scintillation light decay time. This parameter can be extracted online from digitized detector signals. The decay time data are used to eliminate all the temperature determined system gain shifts without radioactive reference source. This technique has been verified in extensive climate chamber measurements. The results are discussed.

Reduction of temperature-dependent gain in L-band EDFA using antimony-aluminum codoped silica EDF

We report a novel technique to suppress the temperature-dependent gain (TDG) of an L-band erbium-doped fiber amplifier. The composite optical gain block consists of conventional L-band erbium-doped fiber (EDF) serially concatenated with a special EDF in a ternary glass composition, antimony-aluminum codoped silica that showed an opposite TDG coefficient in the L-band. The TDG variation of the composite gain block was suppressed to less than /spl plusmn/1.5 dB for a saturated gain of 15 dB between 1565 and 1605 nm, measured over a temperature range of -40/spl deg/C to +80/spl deg/C.

Athermal optical gain block in C-band by serial concatenations of erbium-doped antimony oxide silica glass fiber

We report a new novel technique to suppress the temperature-dependent gain (TDG) of erbium-doped fiber amplifier in the C-band by providing a composite optical gain block, conventional erbium-doped fiber (EDF) serially concatenated with Sb-doped silica EDF. Compared with conventional EDFs, Sb-doped silica EDF showed an opposite TDG coefficient in the C-band. Detailed experimental athermalization schemes are reported for various concatenating configurations. The temperature-dependent optical gain variation was suppressed within /spl plusmn/0.35 dB for the temperature range of -40/spl deg/C to +80/spl deg/C from 1530 to 1560 nm.

L-band EDFA 에서의 온도에 따른 이득 변화와 가변 감쇄기를 이용한 온도 보상

<TEX>$0^{\circ}C$</TEX>에서 5<TEX>$0^{\circ}C$</TEX>까지 온도를 변화시켜 가며 100 GHz의 채널 간격으로 L-band 40채널을 운용했을 때, 온도에 따른 L-band EDFA의 출력 스펙트럼 변화와 이득 변동폭을 측정하였다. 이득 포화 영역에서의 이득의 변화로 인한 출력 스펙트럼의 변화는 온도에 따른 출력 스펙트럼의 변화와 상반되는 점을 이용하여 1단과 2단 사이에 삽입한 가변 감쇄기를 조절하여 온도에 따른 이득 변동을 보상하였다. 그 결과, <TEX>$0^{\circ}C$</TEX>에서 최대 3 dB까지 차이를 보이던 이득 변동 폭은 가변 감쇄기를 이용한 온도 보상으로 1 dB 이내로 줄어듦을 볼 수 있었다. This paper presents a compensation method for a temperature-dependent gain tilt in L-band erbium-doped fiber amplifier using a voltage-controlled attenuator. The gain tilts in the L-band of 1570-1605 nm due to a temperature change have negative slopes, whereas they have positive slopes for the increasing optical input powers in a saturation region. The proposed method utilizes these opposite gain variations to compensate for the gain tilt over a wide range of temperature. While applying forty channels with a channel spacing of 100 GHz in the L-band and changing the ambient temperature from 0 to <TEX>$50^{\circ}C$</TEX>, the compensation method maintained the gain deviation within 1 dB.

Suppression of temperature-dependent gain variation of conventional EDFA by hybrid connection of antimony-doped silica EDF

A new technique to suppress temperature dependence of EDFA gain is proposed and experimentally demonstrated. A specially designed EDF, the glass host of which is Sb-doped silica, showed an opposite sign of temperature dependent gain coefficients in C-band compared to Al-doped silica EDFs. Concatenation of those two EDFs showed an improved gain variation less than /spl plusmn/0.37 dB for the saturated gain over 15 dB, within -40 to +80/spl deg/C.

Correlation of Barrier Height and Nonradiative Carrier Recombination and the Consequences for Optical Gain in GaN Based Laser Structures

We investigated the photoluminescence intensity and material gain values of GaN based laser structures with various well widths in the active layer by temperature dependent photoluminescence and optical gain measurements. The existence of two different nonradiative recombination channels can be demonstrated by temperature dependent photoluminescence measurements at low excitation densities. This results in two thermal activation energies which can be attributed to distinct activation processes. The influence of the nonradiative recombination is also reflected by the temperature dependence of the required material gain values.