QCLs for Gas Sensing in the Mid-IR

Using Wavelength Electronics’ precision temperature controller and low noise Quantum Cascade Laser (QCL) driver, researchers at Princeton University developed a sensor that was designed around a QCL to simultaneously measure nitrous oxide (N2O) and carbon monoxide (CO). The sensor is compact and field-deployable, requiring much less power and having a much smaller footprint and mass than previous sensors, while increasing the accuracy of concentration measurements. The most accurate measurements were 0.15 parts-per-billion-by-volume (ppbv) for N2O and 0.36 ppbv for CO. These accuracies well exceed the requirement of 1 ppbv to be considered “high stability” in the field of atmospheric sensing.

The complete case study is available as CS-LDTC01.

Optoelectronic Qualification: NASA Goddard

The NASA photonics group uses our WLD3343 laser diode drivers and WLD3393 evaluation boards in their optoelectronic qualification set ups. (See http://photonics.gsfc.nasa.gov.)

NASA’s Goddard Space Flight Center supports scientific studies ranging from Earth Science to astrophysics through a variety of missions. Operating the Hubble Space Telescope allows images from the depths of space to be seen. Instruments aboard the Curiosity rover on Mars yield information pertinent to understanding the surface. Satellites under Goddard’s control study the moon, Earth, and sun. (See https://www.nasa.gov/content/goddard-missions-present)

Raman Spectroscopy: Complete Laser Control

The WLD3343 and the WTC3243 are used for complete laser control of a Raman spectrometer.

In order to measure high resolution wave number shifts using Raman spectroscopy, the output of the laser needs to be stable. Providing up to 2.2A of current with 200 ppm stability, the WLD3343 delivers the well-defined current required for this application. Pairing the current source with the WTC3243 temperature controller (stability of 0.0009°C) ensures that the operating temperature of the laser stays consistent, minimizing the effect that temperature fluctuations have on laser output.

Telecomm Manufacturing

A bank of twenty-five PLD12.5K-CHs is used as a fiber splice test system during telecomm laser manufacturing.

Being able to join optical fibers with low loss is important in fiber optic communication. This involves careful cutting of the fibers, precise alignment of the fiber cores, and the fusing of these aligned cores. Fusion splicing is common when a permanent connection is required. In this technique, an electric arc is used to melt the ends of the fibers together. A splice loss estimate is measured by the splicer, by directing light through the cladding on one side and measuring the light leaking from the cladding on the other side.

Medical Lasers

The PLD5K-CH is used to control a surgical laser. The HTC3000 keeps the laser within the appropriate operating temperature.

Laser in situ keratomileusis (LASIK) is the most common procedure for corneal refractive surgery to correct myopia. A focused infrared laser using ultrafast pulses of 100-femtosecond duration is used to create the corneal flap. Adjacent pulses are scanned across the cornea in a controlled pattern without causing significant inflammation or damage to the surrounding tissue.

Portable Shifted Excitation Raman Difference Spectrometer For In-Situ Field Measurements

Shifted Excitation Raman Difference Spectroscopy (SERDS) is proven to minimize the effect of background noise, and reduce measurement time. Now it is moving from the lab to the field. Researchers from Leibniz-Institut für Höchstfrequenztechnik in Berlin present a handheld, highly precise SERDS probe that allows in-situ measurements of chlorophyll in apple leaves.
Read how the stability of the laser system, driven by four LDD400s and temperature controlled by an HTC1500, satisfied the resolution and size requirements of this application.

The complete case study is available as CS-LDTC02.

Methane Detection Using Unmanned Aerial Systems

Researchers from the United States (Princeton University, American Aerospace Technologies) and Germany (Karlsruhe Institute of Technology) have developed a mid-infrared gas-sensing instrument that can be autonomously flown to measure methane levels at different locations and altitudes. To drive the GaSb laser, a Wavelength Electronics LDTC0520 was chosen, because it is small and lightweight enough to mount to a drone or hexacopter while providing the necessary precision.

The complete case study is available as CS-LDTC03.

Utilizing Quantum Dots to Label DNA

By using a modified version of polymerase chain reaction (PCR), researchers from China’s Wuhan University were able to show that one-to-one labeling of DNA with quantum dots could be achieved. Using a Wavelength Electronics LFI3751 temperature controller, thermal testing was done to ensure the stability of the quantum dots during the drastic temperature fluctuations of PCR. This hyper-sensitive labeling scheme can be applied in biology, medicine, and nanomaterial fabrication.

The complete case study is available as CS-TC01.

Trace Atmospheric Gas Sensing with QCLs

Researchers at the Center for Atmospheric and Environmental Chemistry at Aerodyne Research, Inc. have developed a multitude of direct absorption atmospheric trace gas measurement instruments. Relying on high-quality optics, lasers, and electronics, measurements are reaching parts-per-trillion (10-12) precision, in part due to the integrated low-noise current drivers. This precision allows the developed instruments to be viable resources for making realtime measurements of trace atmospheric gases. The use of non-cryogenic semiconductor lasers allows the data to be collected outside of the laboratory in ambient environments.

The complete case study is available as CS-LD01.

Eye-safe Atmospheric Lidar Measurements

The National Center for Atmospheric Research developed an eye-safe aerosol lidar system for atmospheric investigation. Using stimulated Raman scattering (a third-order nonlinear process) the instrument output is eye-safe at approximately 1.5 μm. The instrument has a range of up to 9 km. It also has performance and durability advantages over many previously reported eye-safe lidar configurations. Eye-safe operation is necessary to broaden the available locations for measurements, including more populated areas and near airports.

The system utilized higher pump pulse power than previous implementations. This, in combination with diode laser injection seeding allowed eye-safe lidar measurements of atmospheric composition as a function of both distance and time.

Wavelength’s WLD3343 and WTC3243 were used to control the seed laser. It was crucial to control the seed laser’s output wavelength in order to optimize the beam output. The WLD laser driver paired with the WTC temperature controller allowed for precise tuning of the wavelength.

The complete case study is available as CS-LDTC04.

Laser Diodes in Optofluidics and Microfluidics

Microchips are extremely useful when studying sample sizes less than a milliliter in volume. Researchers from Massachusetts Institute of Technology and Georgia Institute of Technology both used microchips in conjunction with infrared diode lasers to conduct experiments on small-scale environments. The absorption spectrum of water dictated the wavelength choices made by the researchers. On one hand, negligible heating of the water (via absorption) was desired, so the wavelength was chosen away from an absorption peak of water. In the opposite scenario, the laser was utilized to heat up the liquid in the microchip. As such, the wavelength was aligned with a water absorption peak.

In both cases, the laser power delivered to the microchip was a crucial experimental parameter. In each case, the laser driver plays a role in the quality of the output.

The LD5CHA is a next-generation replacement for the PLD5K-CH specified in the Case Study.  The PTC5K-CH can also be paired with the LD5CHA for higher current control than available with the LDTC2/2 cited in the study.

The complete case study is available as CS-LDTC05.

Artery Targeted Photothrombosis to Better Model Human Stroke and Forelimb Impairment

Researchers have developed a better model of human stroke which uses artery-targeted photothrombosis. This model limits laser illumination to specific arterial branches of the cortical surface to induce less damage to surrounding tissue by controlling stability of laser output and minimizing infarct variations. Artery-targeted photothrombosis shows a clear improvement on traditional methods by creating a larger penumbra for a longer amount of time while maintaining the practical results of the traditional model.

When it was essential to have high performance in laser output and stability, researchers turned to the low noise LDD400-1P laser driver. This provided up to 400 mA of current to the laser with noise as low as 5 μA. Laser power stability was crucial in controlling the results and minimizing variability between test subjects regarding infarct size. Because wavelength has been determined to greatly impact the penetration depth of the illumination and noise was the ultimate factor in spatial and temporal resolutions of imaging, the LDD400-1P was the optimal choice to reduce all factors hindering the previous methods/results.

The complete case study is available as CS-LD02.

Frequency-Modulated, LiDAR-Based Length and Thickness Metrology Systems

When manufacturing optics, confirming that they meet specifications is critical. While thickness measurement methods tend to use contact systems that damage the lens and length metrology techniques use methods that have problems with surfaces that diffuse the light, Bridger Photonics provides a solution for both thickness and length applications with a Frequency Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR) technique. Without contact with the optic, Bridger Photonics can measure lengths of up to 2 m and thicknesses of up to 60 mm with 1 µm precision. The FMCW LiDAR Metrology Systems provide additional benefits including three dimensional (3D) mapping with the precision and accuracy needed in laser materials processing applications and optics manufacturing.

The lasers for the FMCW LiDAR need to be wavelength stabilized through precise temperature control because the group index is dependent on wavelength. The WTCP-5V5A can produce temperature stability as low as 0.001ºC. This ensures that the wavelength of the laser does not fluctuate over time.

The complete case study is available as CS-TC02.

Differential Absorption LiDAR for NASA Ozone Mapping

Knowing how much and where ozone is in our atmosphere is important to daily life on Earth. Ozone present in the stratosphere is critical to protecting life from harmful radiation, but ozone in the troposphere is detrimental. NASA has created a network that will allow researchers to analyze potential dangers with ozone levels and propose solutions to these problems. Bridger Photonics has developed a Differential Absorption LiDAR (DIAL) system for this network in a compact, easy-to-use, and commercially available device. With final ultraviolet wavelength energies of 200 μJ (at 1 kHz repetition rate), Bridger Photonics has designed a high power output, low power consumption, and fast repetition rate solution to ozone concentration measurement.

The PTC10K-CH provides stable thermoelectric current to control the temperature of the laser diode arrays and the nonlinear crystal.  The LD15CHA delivers up to 15 A of output current to the laser diode arrays which pump the solid state laser. Because Bridger Photonics operates the driver near limit, it is important that the output current can be set to never exceed the setpoint.

The complete case study is available as CS-LDTC06.

Single-Mode, Narrow Band Photon Source Using SPDC for Hybrid Quantum Systems

Researchers at the University of Vienna have designed a photon source using Spontaneous Parametric Down-Conversion (SPDC) with a doubly resonant Optical Parametric Oscillator (OPO) utilizing an additional birefringent crystal to tune clusters independent of SPDC phase-matching. Achieving the doubly resonant condition in the OPO that enables a single mode is challenging. This photon source has a bandwidth of 10.9 MHz to match the linewidths of atomic transitions. The source also produces single-mode photon pairs at a rate of 47.5 Hz without mode filters reducing loss in the system, which enables research and applications in the quantum realm using hybrid light-matter interactions.

The Optical Parametric Oscillator (OPO) is highly dependent on the temperature of the crystal, which can alter the index of refraction and change the wavelength of the light or change length due to temperature, causing a shift in efficiency and cluster tuning capabilities. Temperature regulation of both crystals in the OPO cavity is essential.  The PTC5K-CH controlled the temperature of the crystals in the OPO cavity with precision better than 2 mK, generating the necessary crystal stability.

The complete case study is available as CS-TC03.

Room Temperature Terahertz Frequency Comb Using QCLs

Researchers at Northwestern University, Illinois have designed a terahertz (THz) frequency comb using a Quantum Cascade Laser (QCL) with a Distributed Feedback (DFB) grating inside the cavity. The DFB grating addition allows for dual wavelength emission from the QCL. A single-mode state and a harmonic comb state combine inside the cavity for a THz frequency comb. Two uses of QCL frequency combs demonstrated by researchers at Harvard University are also discussed.

The QCL’s operation state is highly dependent on the injection current, and the QCLs must be properly and accurately driven with stable temperature control. QCL2000 LAB drivers provide the necessary stability. The PTC10K-CH temperature controller surpasses the required temperature stability of less than 10 mK. At Harvard University, both studies use the TC5 LAB to control the temperature of the QCLs with the same noise levels listed for the Northwestern University study.

The complete case study is available as CS-LDTC07.

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