Long wavelength interband cascade photodetector with type Ⅱ InAs/GaSb superlattice absorber

We report on a long wavelength interband cascade photodetector with type Ⅱ InAs/GaSb superlattice absorber.The device is a three-stage interband cascade structure.At 77 K,the 50%cutoff wavelength of the detector is 8.48μm and the peak photoresponse wavelength is 7.78μm.The peak responsivity is 0.93 A/W and the detectivity D*is 1.12×10^(11)cm·Hz0.5/W for 7.78μm at-0.20 V.The detector can operate up to about 260 K.At 260 K,the 50%cutoff wavelength is 11.52μm,the peak responsivity is 0.78 A/W and the D*is 5.02×10^(8)cm·Hz0.5/W for the peak wavelength of 10.39μm at-2.75 V.The dark current of the device is dominated by the diffusion current under both a small bias voltage of-0.2 V and a large one of-2.75 V for the temperature range of 120 to 260 K.

Relative Chronology in High-Grade Crystalline Terrain of the Eastern Ghats, India: New Insights

The two major lithology or gneiss components in the polycyclic granulite terrain of the Eastern Ghats, India, are the supracrustal rocks, commonly described as khondalites, and the charnockite-gneiss. Northern Eastern Ghats belt, north of the Godavari rift has been defined as the Eastern Ghats Province, while that to the south has been defined as the Ongole domain;and although, these distinct crustal domains also record different ages of granulite metamorphism, both of these domains are dominated by the two lithologies. Many of the workers considered the khondalites as the oldest component with unknown basement and the charnockite- protoliths as intrusive into the khondalites. However, published geochronological data do not corroborate the aforesaid relations. Onset of khondalite sedimentation in the Proterozoic Eastern Ghats Province, constrained by detrital zircon data, as around 1.3 Ga and the charnockite-protolith emplacement between 1.9 and 2.9 Ga, argue against intrusion of felsic magma (tonalite, now enderbite!) in to the khondalites. The field relations of the hornblende-mafic granulite with the two gneiss components together with Sm-Nd isotopic data of the hornblende-mafic granulites (both the xenoliths within charnockites and those interbanded with the khondalites) indicate that khondalite sediments were deposited on older mafic crustal rocks. Mafic basement and supracrustal rocks were subsequently deformed and metamorphosed together during collisional orogeny at high to ultra-high temperatures – partial melting of mafic rocks producing the charnockitic melt;and partial melting of pelitic sediments producing the peraluminous granitoids. This is compatible with all the geochronological data as well as the petrogenetic model of partial melting for the charnockitic rocks in the Eastern Ghats Belt. The Ongole domain, south of the Godavari rift, though, is distinct in terms of the age of first/ earliest UHT metamorphism, but here too the charnockite-protoliths are older mafic rocks evidently not intrusive in to the khondalites.

Visible-Light Excitated Photocatalytic Activity of Rare Earth Metal-Ion-Doped Titania

The rare earth ion Ce 4+ doped TiO 2 was prepared by sol-gel method. The average particle sizes are about 10 nm for sol phase and 55 nm for polycrystalline phase. The photocatalytic activities to degrade Reactive Brilliant Red Dye X-3B were investigated. The result reveals that the spectrum response of Ce 4+-TiO 2 has extended to visible region from the UV region(λ<387 nm) of pure TiO 2. Amorphous phase Ce 4+-TiO 2 sol with an electron scavenger (1.0% atom fraction Ce 4+ ion doping amount) shows the capability of the photocatalytic degradation of the dye X-3B as well as the nanocrystallite Ce 4+-TiO 2 with an interband trap site. Despite of the difference in the morphology of Ce 4+-TiO 2 photocatalyst, there is no apparent difference in respect of the decoloring effects. Whereas, polycrystalline phase Ce 4+-TiO 2 exhibits strong photomineralization power in comparison with the amorphous phase. The photocatalytic oxidation mechanisms of the dye molecule mainly involved in the self-photo-sensitization photolysis process by the first excited singlet oxygen ( 1O 2) and photocatalysis process by hydroxyl radicals(·OH) under visible light irradiation.

Theoretical investigation on near-infrared and visible absorption spectra of nanometallic aluminium with oxide coating in nanoenergetic materials:size and shape effects

The effects of metal core dimension, oxide shell thickness and ellipsoid aspect ratio of Al-Al2O3 core-shell nanoparticles on the near-infrared and visible absorption spectra of nanocomposite Al-Al2O3/nitrocellulose（NC） film are investigated by numerical calculations. Both the size-dependent interband transitions and frequency-dependent free electron damping of the nanometallic aluminium are taken into account in the calculations. Oxidation effect of nanoaluminium is also analysed. It is shown that oxidation may enhance but may also reduce the optical absorption, depending on the excited light energy and initial dimension of nanoparticle. Metal core size and excited light energy dominate the absorption characteristic. The absorption ability of ellipsoidal nanoparticles is larger than that of spheroidal nanoparticles and increases by the square index as the aspect ratio increases. These calculations will provide some significant theoretical guidance for the preparation and laser ignition of nanoenergetic materials.

Room-temperature continuous-wave interband cascade laser emitting at 3.45 μm

We report a type-Ⅱ GaSb-based interband cascade laser operating a continuous wave at room temperature. The cascade region of interband cascade laser was designed using the ‘W' configuration of the active quantum wells and the ‘Carrier Rebalancing' method in the electron injector. The devices were processed into narrow ridges and mounted epitaxial side down on a copper heat sink. The 25-μm-wide, 3-mm-long ridge without coated facets generated 41.4 mW of continuous wave output power at T = 15℃. And a low threshold current density of 267 A/cm^2 is achieved. The emission wavelength of the ICL is 3452.3 nm at 0.5 A.

Room-temperature operating extended short wavelength infrared photodetector based on interband transition of InAsSb/GaSb quantum well

Here in this paper,we report a room-temperature operating infrared photodetector based on the interband transition of an In As Sb/Ga Sb quantum well.The interband transition energy of 5-nm thick In As（0.91）Sb（0.09） embedded in the Ga Sb barrier is calculated to be 0.53 e V（2.35μm）,which makes the absorption range of In As Sb cover an entire range from short-wavelength infrared to long-wavelength infrared spectrum.The fabricated photodetector exhibits a narrow response range from 2.0μm to 2.3μm with a peak around 2.1μm at 300 K.The peak responsivity is 0.4 A/W under-500-m Vapplied bias voltage,corresponding to a peak quantum efficiency of 23.8%in the case without any anti-reflection coating.At 300 K,the photodetector exhibits a dark current density of 6.05×10^-3A/cm^2 under-400-m V applied bias voltage and 3.25×10^-5A/cm^2 under zero,separately.The peak detectivity is 6.91×10^10cm·Hz^1/2/W under zero bias voltage at 300 K.

Influence of intraband motion on the interband excitation and high harmonic generation

Tunnelling, acceleration, and collision of electrons are the basic events in the process of high harmonic generation(HHG) in strong-field interaction with atoms.However, the periodic array of atoms in semiconductor structure makes three steps become interatomic coherent process which leads to complicated carrier dynamics and two sources of high harmonic emission: interband polarization and intraband current.The difference of features of high harmonic generation between semiconductors and atoms is strongly linked to the unique presence of intraband motion which manifests itself a nontrivial role in intertwined two dynamics.Here, we review recent experimental and theoretical advances of understanding coupled interband and intraband mechanisms of HHG in semiconductors.Particularly we focus on the influence of intraband motion on the interband excitation, and on the subsequent HHG emission and attosecond pulse generation.

A method to extend wavelength into middle-wavelength infrared based on InAsSb/(Al)GaSb interband transition quantum well infrared photodetector

We present a method to extend the operating wavelength of the interband transition quantum well photodetector from an extended short-wavelength infrared region to a middle-wavelength infrared region. In the modified In As Sb quantum well, Ga Sb is replaced with Al Sb/Al Ga Sb, the valence band of the barrier material is lowered, the first restricted energy level is higher than the valence band of the barrier material, the energy band structure forms type-II structure. The photocurrent spectrum manifest that the fabricated photodetector exhibits a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78 K.

Quantifying plasmon resonance and interband transition contributions in photocatalysis of gold nanoparticle

Localized surface plasmon has been extensively studied and used for the photocatalysis of various chemical reactions.However,the different contributions between plasmon resonance and interband transition in photocatalysis has not been well understood.Here,we study the photothermal and hot electrons effects for crystal transformation by combining controlled experiments with numerical simulations.By photo-excitation of Na YF4:Eu^(3+)@Au composite structure,it is found that the plasmonic catalysis is much superior to that of interband transition in the experiments,owing to the hot electrons generated by plasmon decay more energetic to facilitate the reaction.We emphasize that the energy level of hot electrons plays an essential role for improving the photocatalytic activity.The results provide guidelines for improving the efficiency of plasmonic catalysis in future experimental design.

Influence of Polar Pressure Transmission Medium on the Pressure Coefficient of Excitonic Interband Transitions in Monolayer WSe_2

The influence of the pressure transmission medium（PTM）on the excitonic interband transitions in monolayer tungsten diselenide（WSe2）is investigated using photoluminescence（PL）spectra under hydrostatic pressure up to 5GPa.Three kinds of PTMs,condensed argon（Ar）,1：1 n-pentane and isopentane mixture（PM）,and4：1 methanol and ethanol mixture（MEM,a PTM with polarity）,are used.It is found that when either Ar or PM is used as the PTM,the PL peak of exciton related to the direct K-K interband transition shows a pressure-induced blue-shift at a rate of 32±4 or 32±1 meV/GPa,while it turns to be 50±9meV/GPa when MEM is used as the PTM.The indirect A-K interband transition presents almost no shift with increasing pressure up to approximatel.y 5 GPa when Ar and PM are used as the PTM,while it shows a red-shift at the rate of-17±7meV/GPa by using MEM as the PTM.These results reveal that the optical interband transitions of monolayer WSe2 are very sensitive to the polarity of the PTM.The anomalous pressure coefficient obtained using the polar PTM of MEM is ascribed to the existence of hydrogen-like bonds between hydroxyl in MEM and Se atoms under hydrostatic pressure.

ZTE Debuts LTE-A InterBand Dual-Carrier Commercial Base Station at MWC

ZTE debuted its LTEA interband dualcarrier commercial base station at the Mobile World Congress 2012 （MWC 2012） in Barcelona on February 27, 2012.

FDD单天线多组合载波聚合解决方案

载波聚合能利用不连续的频谱资源,聚合为载波资源,提高频谱的利用率,增加信号带宽,提高信号的传输速度。不同的运营商采用的载波聚合的形态不同,终端所能支持的载波聚合形态要尽可能多。基于此,在主天线采用单天线的终端系统中,采用分离滤波器、四工器、DoubleFilter或者TripleFliter替代传统的双工器,实现多种组合载波聚合。

Hot hole multiplication from silver plasmon-resonated gold interband transitions for enhanced photoelectrochemical sensing

Compared with the widespread exploitation of hot electrons in plasmonic nanoparticles(NPs),hot holes generated from plasmonic metal interband transitions,are often overlooked in photoelectrochemistry,including photoelectrochemical sensing.Motivated by the subtle spectral overlap between the characteristic plasmonic bands of Ag NPs and interband transitions of Au,herein,we construct unusual core-shell Ag@Au NPs via an anti-galvanic reaction to promote the generation of hot holes.Benefiting from the unique plasmon resonances of Ag cores in specific wavelength regimes,Ag@Au can excite multiplied hot holes while Au cannot under the same conditions.With satisfactory accuracy and good practicability,the photoelectrochemical sensing platform based on Ag@Au NPs possesses a detection limit of 77 nmol/L for glucose,exhibiting significantly higher sensitivity compared to that using Au NPs.This work exemplifies the applications of interband hot-hole accumulation initiated by plasmons and may inspire more strategies to explore the utilization of hot holes in photoelectrochemistry.

Origin of strong and narrow localized surface plasmon resonance of copper nanocubes

Inexpe nsive copper nano particles are generally thought to possess weak and broad localized surface plasm on resonance(LSPR).The,present experimental and theoretical studies show that tailoring the Cu nanoparticle to a cubic shape results in a single intense,narrow,and asymmetric LSPR line shape,which is even superior to round-shaped gold nanoparticles.In this study,the dielectric function of copper is decomposed into an interband transition component and a free-electron component.This allows interband transition-induced plasmon damping to be visualized both spectrally and by surface polarization charges.The results reveal that the LSPR of Cu nanocubes originates from the comer mode as it is spectrally separated from the interb and transitions.In additi on,the interband tran sitions lead to severe damping of the local electromagnetic field but the cubic corner LSPR mode survives.Cu nanocubes display an extinction coefficient comparable to the dipole mode of a gold nanosphere with the same volume and show a larger local electromagnetic field enhancement These results will guider-development of in expensive plasmonic copper-based nano materials.

InAs-based interband cascade lasers at 4.0 μm operating at room temperature

InAs-based interband cascade lasers（ICLs） with InAs plasmon waveguides or InAs/AlSb superlattice（SL） waveguides were demonstrated at emission wavelengths below 4.1 μm. The threshold current densities of the lasers with SL waveguides were 37 A/cm;at 77 K in continuous wave mode. The operation temperature of these lasers reached room temperature in pulsed mode. Compared with the thick InAs n++ plasmon cladding layer, the InAs/AlSb superlattice cladding layers have greater advantages for ICLs with wavelengths less than 4 μm even in InAs based ICLs because in the short-wavelength region they have a higher confinement factor than InAs plasmon waveguides.

Theoretical simulation of T2SLs InAs/GaSb cascade photodetector for HOT condition

The investigation of the interband type-II superlattice In As/Ga Sb cascade photodetector in the temperature range of 320–380 K is presented. The article is devoted to the theoretical modeling of the cascade detector characteristics by the use of the Simu Apsys platform and the 4-band model（k·p 8 × 8 method）. The obtained theoretical characteristics are comparable with experimentally measured ones, suggesting that transport in the absorber is determined by the dynamics of intrinsic carriers and by their lifetime. An overlap equal to 120 me V was used in calculations and a correction term in the ＂non-common atom＂ model Hxy = 700 me V was added to the Hamiltonian. The electron and hole effective masses from dispersion curves were estimated and absorption coefficient α was calculated. Based on the simulation detectivity, D＊ characteristics in the temperature range 320–380 K were calculated. The simulated theoretical characteristics at 320 K are comparable to experimentally measured ones, however at higher temperatures, the experimental value of D＊ does not reach the theoretical values due to the low resistance of the device and short diffusion length.

Detection of Ethanol Using a Tunable Interband Cascade Laser at 3.345μm

With the progress of the laser manufacturing technology, trace gas sensors based on tunable interband cascade lasers （ICLs） and quantum cascade lasers （QCLs） have been widely used to detect organic compounds with high sensitivity. Compared with overtone and combination bands in the near infrared region, for many species, the intensities of fundamental rotational-vibrational absorption bands in the mid-infrared region are much stronger. In this paper, we demonstrate an ethanol sensor using a room-temperature continuous-wave （CW） tunable ICL laser as a light source to detect ethanol vapor concentration with high sensitivity. Combined with the first harmonic （1 f） normalized second harmonic （2f） wavelength modulation spectroscopy （WMS） technology, the characteristics of the harmonics of the system are analyzed, and the amplitude of the first harmonic decrease with an increased concentration of ethanol has been demonstrated both theoretically and experimentally. As a result, a detection limitation of 28 ppb is achieved.

Multistage interband cascade photovoltaic devices with a bandgap of 0.23 eV operating above room temperature

Interband cascade(IC)photovoltaic(PV)device structures,consisting of multiple discrete InAs/GaSb superlattice absorbers sandwiched between electron and hole barriers,were grown by molecular beam epitaxy.Details of the molecular beam epitaxy growth and material characterization of the structures are presented.The discrete absorber architecture enables certain advantages,such as high open-circuit voltage,high collection efficiency,high operating temperature,and smooth integration of cascade stages with different bandgaps.The two-and three-stage ICPV devices presented in this article operate at room temperature with substantial open-circuit voltages at a cutoff wavelength of 5.3 lm(corresponding to a bandgap of 0.23 eV),the longest ever reported for room temperature PV devices.The device characteristics indicate a high level of current matching and demonstrate the advantages of the interband cascade approach in thermophotovoltaic cell design.

Interband cascade lasers with short electron injector

We demonstrate Ga Sb-based interband cascade lasers(ICLs) emitting around 3.65 μm, which exhibit a room-temperature continuous-wave(CW) output power above 100 m W. Cavity-length analysis showed that the laser structure has a low internal loss of 3 cm^(-1) while maintaining a total internal quantum efficiency greater than one. After 6400 h CW operation at 25°C,the threshold current of the laser increased by 3%, and the output power decreased by 7%, indicating good reliability of the device.

Dielectric confinement on exciton binding energy and nonlinear optical properties in a strained Zn_(1-x_(in))Mg_(x(in))Se/Zn_(1-x(out))Mg_(x(out))Se quantum well

The band offsets for a Zn1-xin Mgxin Se/Zn1-xout Mgxout Se quantum well heterostructure are determined using the model solid theory. The heavy hole exciton binding energies are investigated with various Mg alloy contents. The effect of mismatch between the dielectric constants between the well and the barrier is taken into account. The dependence of the excitonic transition energies on the geometrical confinement and the Mg alloy is discussed. Non-linear optical properties are determined using the compact density matrix approach. The linear, third order non-linear optical absorption coefficient values and the refractive index changes of the exciton are calculated for different concentrations of magnesium. The results show that the occurred blue shifts of the resonant peak due to the Mg incorporation give the information about the variation of two energy levels in the quantum well width.