Interband Cascade Lasers Research Articles

Sensitive acetone detection with a mid-IR interband cascade laser and wavelength modulation spectroscopy

An efficient method for the detection of acetone, an important biomarker in exhaled breath, by utilizing wavelength modulation spectroscopy (WMS) with a mid-infrared distributed feedback interband cascade laser (DFB-ICL) is presented. The performance of the DFB-ICL laser is characterized, and its linewidth is measured to be $\mbox{(3}.\mbox{39} \pm 0.\mbox{15)}$(3.39±0.15) MHz by beating the output with an auxiliary mid-IR frequency comb over 50 ms. The measured asymmetric acetone absorption profile with the center wavelength around 3367 nm is fitted by the pseudo-Voigt function. The phase shift between the intensity and frequency modulations is determined and used for processing the results. The sensor is tested by performing measurements with calibration mixtures of acetone in nitrogen, and the detection limits of 0.58 ppm and 0.12 ppm were determined with 1 s and 60 s signal averaging times, respectively. Our work shows that wavelength modulation spectroscopy with a DFB-ICL laser complimented by a multipass cell for higher sensitivity can be efficiently used for acetone detection and is promising for sensitive breath analysis.

ICL-based mid-infrared carbon dioxide sensor system for deep-sea natural gas hydrate exploration.

For deep-sea natural gas hydrate exploration, highly sensitive detection of the dissolved gas in seawater near the seabed is significant because it requires the sensor system to be small in size, low in power consumption, and high in sensitivity. A mid-infrared sensor system was developed to detect dissolved carbon dioxide (CO2) in sea-water, while employing a 4319 nm continuous-wave interband cascade laser (ICL) and a multi-pass gas cell (MPGC) with a 29.8 m optical path length. A compact rectilinear optical structure was proposed by using the free-space-emitting ICL and tunable laser absorption spectroscopy (TLAS). This leads to a minimized sensor size and a simple optical alignment for deep-sea operation. A strong CO2 absorption line, located at 2315.19 cm-1 and a weak 2315.28 cm-1 line and at a low pressure of 40 Torr, was targeted for low- and high-concentration CO2 detection within a concentration range of 0-1000 parts per billion by volume (ppbv) and 0-40 parts per million by volume (ppmv), respectively. The limit of detection (LoD) was assessed to be 0.72 ppbv at an averaging time of 2 s, and the response time was measured to be ~30 s at a flow rate of ~180 standard cubic centimeters per minute (sccm). Deployment of the CO2 sensor combined with a gas-liquid separator was carried out for the CO2 detection in the gas extracted from water, which validated the reported sensor system's potential application for deep-sea natural gas hydrate exploration.

High resolution spectra of 13C ethane and propane isotopologues photoacoustically measured using interband cascade lasers near 3.33 and 3.38 µm, respectively

We report measurements of short-chained hydrocarbon isotopologues using two continuous wave (cw), thermoelectrically cooled (TEC), distributed feedback interband cascade lasers (DFB-ICLs) around 3.33 and 3.38 µm. The high resolution absorption spectra of 12CH3-13CH3, 13CH3-13CH3 and 12CH3-12CH2-13CH3 were recorded at room temperature and atmospheric pressure for concentrations of approximately 0.1% in nitrogen using photoacoustic spectroscopy (PAS). For calibration and analysis purposes the 13C spectra as well as ethane and propane spectra at natural abundance are compared to respective FTIR spectra originating from the HITRAN database and results of a previous study. The high resolution absorption spectra will allow isotopologue-sensitive spectral analyses of ethane and propane in this spectral region and may be used as reference data for applications from atmospheric and planetary research to natural gas exploration.

The driver design for N2O gas detection system based on tunable interband cascade laser

In this paper, the driver circuit for N2O gas detection system based on tunable interband cascade laser (ICL) is developed. Considering the influence of power supply stability on the digital-analog hybrid drive circuit of tunable diode laser absorption spectroscopy (TDALS), the high-efficiency TPS5430 is used to design the positive and negative power supply circuit. The large electrolytic capacitor + post-stage LC filter combination filter is used to effectively filter out high and low frequency ripple and switching noise. The use of thick high current trace + via + multilayer printed circuit board (PCB) design makes the line temperature rise smaller, more stable and durable, and uses high frequency shielding inductance to effectively reduce radiation interference to ensure the stability of the drive. The STM32F407, a highperformance microcontroller based on the ARM Cortex-M4 core, is used as the master control chip and generates a sawtooth scanning signal. The direct digital synthesizer (DDS) chip ICL8038 is used to generate a sinusoidal modulated signal of a specific frequency. The two signals are superimposed by a reverse addition circuit, and the laser drive signal is generated by a developed positive feedback balanced voltagecurrent conversion circuit. Experimental results show that the driver circuit can well meet the drive development requirements of N2O gas detection systems based on tunable interband cascade laser.

Double-waveguide interband cascade laser with dual-wavelength emission

Interband cascade lasers (ICLs) with dual wavelength emission have been realized by utilizing two spatially separated active regions in the same device. The two wavelengths (3.1 and 3.7 μm) were chosen in order to demonstrate that the usual spectral gain bandwidth of an ICL can be overcome. At 20 °C, threshold current densities as low as 215 A/cm2 (short wavelength) and 158 A/cm2 (long wavelength) could be achieved in the pulsed mode. It was possible for an epi-up mounted device to maintain dual-wavelength continuous-wave emission up to 0 °C. Despite the longer wavelength emission being suppressed at higher temperatures, the shorter wavelength maintained an output power of more than 10 mW at 15 °C.

M-shaped quantum wells for active region of interband cascade laser

This work proposes an M-shaped design of quantum wells (QWs) based on a combination of InAs and GaInSb materials forming a broken gap type II system, which can be used as an active region of interband cascade lasers emitting in the mid infrared. Results of band structure modelling revealed that compared to more common W-shaped QWs, the M-design can offer some advantages. For instance, there can be obtained a significant electrical tunability of optical transitions oscillator strength and hence also characteristic lifetimes, which would make such structures beneficial in construction of passively mode-locked laser devices.

Performance Enhancement of Methane Detection Using a Novel Self-Adaptive Mid-Infrared Absorption Spectroscopy Technique

An electrical-domain self-adaptive mid-infrared absorption spectroscopy for methane detection based on an interband cascade laser was demonstrated. By adding noise into the laser drive signal, denoising and sensing performances were evaluated for the technique. Experiments were made to study the effects of noise level/type on sensor stability, characterized by Allan deviation. High- and low-frequency noise levels have the same functional variation trend on Allan deviation, which differs from white Gaussian noise. Within a noise level range of 0–125 mV for low- and high-frequency noise and 0–62.5 mV for white Gaussian noise in the mercury–cadmium–telluride detector's output (with a pure signal amplitude of ∼300 mV), the sensor stability using self-adaptive denoising was enhanced by a factor of 1.05–20, 1.32–6.25, and 1.15–3.33 times compared to that using no filtering, for the three kinds of noise, respectively. The reported self-adaptive methane sensor system shows enhanced stability compared to the direct laser absorption spectroscopy sensor using traditional sensing architecture and classic filtering method. The sensor was further evaluated through outdoor atmospheric methane measurements using such technique. A second-order self-adaptive direct laser absorption spectroscopy technique was also proposed for noise suppression in both optical and electrical domain as an outlook of the concept of this paper.

Methane, ethane and propane detection using a compact quartz enhanced photoacoustic sensor and a single interband cascade laser

Hydrocarbon detection in the gas phase represents a powerful tool to guide oil exploration and production operations for the oil & gas industry. This application requires highly sensitive, selective and robust spectroscopic techniques. In this work, a quartz-enhanced photoacoustic sensor system designed to detect methane (C1), ethane (C2) and propane (C3), employing a single interband cascade laser emitting in the spectral range 3.342–3.349 μm, is reported. Detection levels in the part-per billion concentration range for C1 and C2 and a few parts per million for C3 were achieved. Measurements at both low and atmospheric pressures were carried out for mixtures simulating typical downhole hydrocarbon concentrations.

Room-temperature continuous-wave interband cascade laser emitting at 3.45 μm**Project supported by the Major Program of the National Natural Science Foundation of China (Grant No. 61790580), the National Natural Science Foundation of China (Grant No. 61435012), and the National Basic Research Program of China (Grant No. 2014CB643903).

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 °C. And a low threshold current density of 267 A/cm2 is achieved. The emission wavelength of the ICL is 3452.3 nm at 0.5 A.

InAs-based interband cascade lasers at 4.0 μm operating at room temperature * * Project supported by the National Natural Science Foundation of China (Nos. 61790583, 61774150, 61774151) and the National Basic Research Program of China (No. 2014CB643903).

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/cm2 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.

A Trace C₂H₂ Sensor Based on an Absorption Spectrum Technique Using a Mid-Infrared Interband Cascade Laser.

In this study, tunable diode laser absorption spectroscopy (TDLAS) combined with wavelength modulation spectroscopy (WMS) was used to develop a trace C2H2 sensor based on the principle of gas absorption spectroscopy. The core of this sensor is an interband cascade laser that releases wavelength locks to the best absorption line of C2H2 at 3305 cm−1 (3026 nm) using a driving current and a working temperature control. As the detected result was influenced by 1/f noise caused by the laser or external environmental factors, the TDLAS-WMS technology was used to suppress the 1/f noise effectively, to obtain a better minimum detection limit (MDL) performance. The experimental results using C2H2 gas with five different concentrations show a good linear relationship between the peak value of the second harmonic signal and the gas concentration, with a linearity of 0.9987 and detection accuracy of 0.4%. In total, 1 ppmv of C2H2 gas sample was used for a 2 h observation experiment. The data show that the MDL is low as 1 ppbv at an integration time of 63 s. In addition, the sensor can be realized by changing the wavelength of the laser to detect a variety of gases, which shows the flexibility and practicability of the proposed sensor.

Temperature-dependent line parameter study of acetylene transitions near 3 µm

Knowledge of the acetylene spectrum is important for astrophysics, atmospheric, and combustion chemistry research. Twelve acetylene transitions across eleven bands have been studied between 3335.0 and 3336.5 cm−1 with a tunable interband cascade laser. Linestrengths and temperature-dependent lineshape parameters, including collisional broadening and narrowing, are reported through Voigt, Rautian, and Galatry lineshape fits to two strong cold band transitions. Measurements were made in pure acetylene, as well as with diluents argon, nitrogen, and methane, over a temperature range of 296–637 K and pressures of 5–90 Torr. Linestrengths and temperature-dependent self-broadening coefficients are also reported for ten weak hot band transitions through Voigt lineshape fits, measured between 296–513 K and 5–20 Torr. Line parameter measurements are found to be in good agreement with the literature and extend experimental lineshape studies of acetylene into new rovibrational bands, a sparsely-studied temperature regime, and a new perturber: methane.

Real-Time and Simultaneous Monitoring of NO, NO2, and N2O Using Substrate-Integrated Hollow Waveguides Coupled to a Compact Fourier Transform Infrared (FT-IR) Spectrometer.

Nitrogen-based fertilizers have been used in modern agricultural activities resulting in a relevant emission source of nitrogen gases into the atmosphere, mainly nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O). Furthermore, the burning of fossil fuels is the most significant emission source of NOx (i.e., NO + NO2), being the controlling of vehicle exhaust system an essential task. Those compounds can be related to air pollution effects either directly, by emitting a powerful greenhouse gas (i.e., N2O), or indirectly, by formation of nitric acid (HNO3) or ammonium nitrate (NH4NO3) from NO or NO2, responsible for the increase of acid rain and particulate material into the atmosphere. This context requires appropriate sensor technology facilitating in situ and simultaneous monitoring of nitrogen emitted gases, with easiness of operation and compact dimensions. In this communication, we describe an innovative mid-infrared chemical sensor platform for the in situ, real-time, and simultaneous quantification of gaseous NO, NO2, and N2O by combining a compact Fourier transform infrared (FT-IR) spectrometer with the so-called substrate-integrated hollow waveguide (iHWG) as a miniaturized gas cell. The optical platform enabled limits of detection of 10, 1, and 0.5 ppm of NO, NO2, and N2O, respectively. The linear concentration range evaluated in this study is suitable for the application of the sensing platform in vehicle exhaust air samples. Given the high adaptability of the developed infrared sensing device toward preconcentration or ultraviolet conversion modules and also considering the potential for combining tunable interband cascade lasers (ICLs) in lieu of the FT-IR spectrometer, we anticipate the application of the sensing platform for in situ determination of nitrogen gases in a wide range of scenarios.

Measurement of Atmospheric Dimethyl Sulfide with a Distributed Feedback Interband Cascade Laser.

This paper presents a mid-infrared dimethyl sulfide (CH3SCH3, DMS) sensor based on tunable laser absorption spectroscopy with a distributed feedback interband cascade laser to measure DMS in the atmosphere. Different from previous work, in which only DMS was tested and under pure nitrogen conditions, we measured DMS mixed by common air to establish the actual atmospheric measurement environment. Moreover, we used tunable laser absorption spectroscopy with spectral fitting to enable multi-species (i.e., DMS, CH4, and H2O) measurement simultaneously. Meanwhile, we used empirical mode decomposition and greatly reduced the interference of optical fringes and noise. The sensor performances were evaluated with atmospheric mixture in laboratory conditions. The sensor’s measurement uncertainties of DMS, CH4, and H2O were as low as 80 ppb, 20 ppb, and 0.01% with an integration time 1 s, respectively. The sensor possessed a very low detection limit of 9.6 ppb with an integration time of 164 s for DMS, corresponding to an absorbance of 7.4 × 10−6, which showed a good anti-interference ability and stable performance after optical interference removal. We demonstrated that the sensor can be used for DMS measurement, as well as multi-species atmospheric measurements of DMS, H2O, and CH4 simultaneously.

Interband cascade laser absorption sensor for real-time monitoring of formaldehyde filtration by a nanofiber membrane.

It is important to reduce the indoor formaldehyde (H2CO) level to improve indoor air quality. To investigate the H2CO filtration by a novel nanofiber membrane made from metal-organic frameworks (MOFs), we developed a laser absorption gas sensor for real-time H2CO monitoring using a room-temperature interband cascade laser (ICL) emitting at 3.6µm. Wavelength modulation spectroscopy combined with a multipass gas cell (36m path length) was implemented to achieve a detection sensitivity of 3ppb H2CO at 1-s averaging time. We custom-designed a permeation H2CO generator that produces reference H2CO/N2 mixtures with an uncertainty of 6.4% in concentration. With the time-resolved continuous measurements, we observed a high filtration efficiency of 83% for the MOF filter, which, however, decreases linearly to 30% after operating for 3h. Hence, the ICL-based gas sensor has proved to be a promising technique to assess novel nanomaterials for indoor air purification and pollutant control applications.

Double-pass Co:CdTe mid-infrared laser amplifier

Mid-infrared optical gain has been successfully demonstrated by cobalt-doped cadmium telluride using a double-pass amplification technique. A 3.7 µm interband cascade laser was amplified by resonantly pumping Co:CdTe with a 2.8 µm continuous-wave Er-fiber laser. Cobalt-doped-chalcogenide gain media have been of considerable interest because they emit within the 3 – 5 µm atmospheric transmission window, contain broad emission characteristics and have relatively long radiative lifetimes. A measurable gain of 2.8 on the 4A2 ↔ 4T2 transition is reported.

Interband cascade laser on silicon

Mid-infrared (MIR) silicon photonic systems show great promise for miniaturizing a variety of sensing and detection technologies. Rapid progress has been made in recent years, and numerous passive and active MIR devices have now been constructed on various silicon-based platforms. We previously reported the heterogeneous integration on silicon of Fabry–Perot and distributed feedback quantum cascade lasers (QCLs) operating at 4.8 μm. Interband cascade lasers (ICLs) will be preferred for many on-chip sensing technologies because they operate in the 3–6 μm range with threshold drive powers 1–2 orders of magnitude lower than QCLs. In this work, we demonstrate the integration of ICLs on a silicon substrate. These lasers emit 3.6 μm light into silicon-on-insulator waveguides in pulsed mode at temperatures up to 50°C. This represents an important step toward MIR photonic integrated circuits on silicon that operate with much lower drive power and therefore an even smaller footprint.

Metrological quantification of CO in biogas using laser absorption spectroscopy and gas chromatography

Biogas has a vital role in the future market for renewable energy. When upgraded to biomethane, it can be injected into natural gas grids if the level of certain impurities complies with the specifications in EN16723. For some of these impurities, suitable measurement methods are lacking which hamper the quality control of biomethane to be injected into natural gas networks. Here, we report on the evaluation of three detection methods suitable for carbon monoxide (CO) in biogas and biomethane applications for which EN16723 specifies an upper limit of 0.1% (1000 µmol ⋅ mol−1). Two of these methods are based on laser absorption spectroscopy (LAS) and one on gas chromatography (GC). Both LAS spectrometers employ direct absorption spectroscopy and operate at 4.6 µm, probing a single CO absorption line in the fundamental CO band. One of them, direct tunable diode laser absorption spectroscopy (dTDLAS), is based on a new interband cascade laser specially designed for biogas and biomethane applications, while the other is based on quantum cascade laser absorption spectroscopy (QCLAS). The GC is equipped with two packed columns (HayeSep Q and molecular sieve 5A) and a thermal conductivity detector. CO amount fraction results in biogas matrices derived using these three measurement methods and are compared to amount fraction values of different, gravimetrically prepared reference gas standards of CO in biogas. These were used to validate the measurement capabilities. The measured CO amount fraction results from LAS and GC covered 10–30 000 µmol ⋅ mol−1 (system measurement ranges, LAS: 3–1000 µmol ⋅ mol−1, GC: 500–30 000 µmol ⋅ mol−1) and were in excellent agreement with the gravimetric values of the gas standards. At 400 µmol ⋅ mol−1, the guide to the expression of uncertainty in measurement compliant relative standard uncertainties of our calibration-free dTDLAS and the gas-calibrated QCLAS systems are estimated to be 1.4% versus 0.5%, respectively. The relative standard uncertainty of the GC CO measurements at 5075 µmol ⋅ mol−1 is 1.3%. This work demonstrates that, by means of GC and LAS, relative standard uncertainties of 1.4% and below can be reached for CO measurements in biogas and that cost-optimized calibration-free approaches not requiring frequent use of gas standards have become available.

Advanced Photonic Sensors Based on Interband Cascade Lasers for Real-Time Mouse Breath Analysis.

A multiparameter gas sensor based on distributed feedback interband cascade lasers emitting at 4.35 μm and ultrafast electro-spun luminescence oxygen sensors has been developed for the quantification and continuous monitoring of 13CO2/12CO2 isotopic ratio changes and oxygen in exhaled mouse breath samples. Mid-infrared absorption spectra for quantitatively monitoring the enrichment of 13CO2 levels were recorded in a miniaturized dual-channel substrate-integrated hollow waveguide using balanced ratiometric detection, whereas luminescence quenching was used for synchronously detecting exhaled oxygen levels. Allan variance analysis verified a CO2 measurement precision of 1.6‰ during a 480 s integration time. Routine online monitoring of exhaled mouse breath was performed in 14 mechanically ventilated and instrumented mice and demonstrated the feasibility of online isotope-selective exhaled breath analysis within microliters of probed gas samples using the reported combined sensor platform.

Detection of Ethanol Using a Tunable Interband Cascade Laser at 3.345 \u03bcm

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 (1f) 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.