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.

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