APPLICATION NOTE: Modulation Basics

Modulation can be useful for a variety of applications: the capacity of transmitted data can be increased with high frequency sources and modulators; risk of eye damage can be reduced and sensitivity of LIDAR measurements optimized; and in spectroscopy, modulated lasers can provide fast data acquisition, reduce the system costs, and enable high resolution without damaging the sample.

This application note discusses the different types of modulation, their benefits and limitations, important design parameters for modulation, and some best practices for resolving modulation issues.

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A potential method to distinguish individual sources of methane emission is to measure the ratios of isotopologues in the environment compared to standard compositions. The use of mid-infrared (MIR) quantum cascade lasers (QCL) generates high precision, high spectral purity, and high optical power in continuous wave operation at room temperature. This enables a compact design with potential parts-per-trillion measurements while eliminating the need for flask sampling. Researchers from Switzerland, the Netherlands, Germany, and the UK have developed a quantum cascade laser absorption spectrometer (QCLAS) coupled with a trace gas extractor (TREX) for high precision measurements of methane isotopologues in ambient air. When compared to popular techniques of isotope mass-ratio spectrometry and other laser spectroscopy, the TREX-QCLAS has similar results with less labor-intensive features and automated real-time analysis for in situ measurements to better identify different emission sources.

Due to the high precision demands of the spectrometer, researchers upgraded the electronic equipment to utilize Wavelength Electronics’ high performance QCL drivers and temperature controllers. These critical components enable the sensitive measurements and analysis of methane isotopologues. For the researchers, “laser operation stability is of utmost importance” highlighting the need for ultra-low noise laser drivers.

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Polymerase Chain Reaction (PCR) enables amplification of a specific deoxyribonucleic acid (DNA) region between two regions of known DNA sequence. Through precise heating and cooling steps, DNA can be replicated in an exponential manner. PCR can be used for genotyping, cloning, mutation detection, sequencing, microarrays, forensics, and paternity testing. Researchers have developed a PCR thermal cycler using a proportional-integral (PI) temperature controller. The high performance temperature controller provides the fast temperature ramp rate, minimal temperature overshoot, and tight temperature stability necessary for rapid temperature changes in the PCR process. The temperature controller, as well as other commercial off-the-shelf products, reduce prototyping costs and maintain accurate and precise reactions. This portable and low-cost thermal cycler allows better opportunities for low-resource areas compared to the bulky and expensive commercial devices available.

Wavelength Electronics’ PTC10K-CH temperature controller was used to control the PCR block temperature. Optimizing the proportional gain setting optimized block stability. Using Wavelength Electronics’ PTC10K-CH, researchers were able to develop a thermal cycler with a faster temperature ramp rate and lower overshoot. Because the PCR process is heavily temperature dependent, accurate and precise temperature control is essential.

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Photonteck Company is the fastest growing Distributor we have. Our partnership started in 2007 as our Chinese Distributor, and their service is impressive. Aaron Wang leads the laser applications team as the Product Director and Robin Wu is the Product Manager. With their headquarters in Wuhan, they also have offices in Shenzhen, Hong Kong, Suzhou, and Chengdu for their 100+ employees. They have a hands-on approach with all their customers and want to see the small customers grow as much as their large customers. They offer the same service to everybody and feel if the customers succeed then Photonteck will also succeed.

Photonteck goes beyond all expectations. During the COVID-19 pandemic they made sure to send us masks for our employees and their families, not once, but twice just to make sure we were all protected. Also, during the pandemic when many people were home all over the world, Robin Wu helped us test LAB instrument functionality from his home to help us with a revision. These are just a few examples of how Photonteck sets their company apart from all the rest. It is our honor and privilege to call them partners and call them our friends.

Photonteck provides a deep understanding of the whole vertical chain of the fiber-optical communication industry in China, and insight into a variety of resources ranging from raw material supply, through R&D resources, to manufacturing capability & quality control.

Visit the Photonteck website.

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