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Photodigm Laser Blog

High Power, Single-Frequency Monolithic Laser Diodes for Precision Applications


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Informally discussing single spatial and single longitudinal mode laser diodes

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"Real Men Have Fabs" works for semiconductor lasers too

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

This provacative and iconic statement made by AMD founder Jerry Sanders in the 1980's, was intended to drive a stake in the ground about competitive advantage in the semiconductor industry.  The 1980's were a time of tremendous turmoil in the industry.  The low cost of Japanese capital fueled a fab boom in Japan that threatened the existence of the US semiconductor industry. The American industry had gone through several boom and bust cycles, and the Japanese industrial base was threatening the American base. DRAMs were showing some signs of maturity, and some were calling manufacturing a commodity skill that was best done in Asia.  Others were arguing the opposite.  Jerry Sanders was clear where he and his company stood.  

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Wavelength Tuning in Distributed Bragg Reflector Lasers

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

DBR schematic

Deterministic wavelength tunability is a key advantage of Photodigm's monolithic DBR lasers. Applications requiring the precision of distributed Bragg reflector laser diodes are becoming more and more demanding in terms of power and mode purity.  In pulsed applications, wavelength agility, stability, and peak power are critical performance parameters. Spectroscopic analysis requires a wavelength scan across the spectral feature to resolve it. The narrow bandwidth and tunability of the DBR laser enables extremely high resolution over a narrow portion of the spectrum, opening up spectroscopic applications not available to conventional slit based spectrometers.   Furthermore, by repetitively scanning across the feature, an error signal can be generated that allows locking of the laser output to a specific transition.  

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Second Harmonic Generation with DBR Lasers

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

Second Harmonic Generation

One of the first applications for Photodigm’s single frequency, diffraction limited DBR lasers was second harmonic generation (SHG) for an RGB laser projection module. This was in the days around 2004 when the big box consumer electronics showrooms were filled with large rear projection televisions. Laser projection was seen as a way to compete against the svelte but expensive flat panel models. The low etendue of the diffraction limited laser beam would compress the optical path, and the semiconductor scalability of laser diodes offered an economic competitor to the short-lived high intensity discharge lamps that illuminated most of the volume on the showroom floor.  After all, the lamp was the costliest and least reliable element of the BOM in those sets of the early 2000’s. 

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Tunable Laser Diodes in the Undergraduate Atomic Physics Lab

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

Photodigm DBR lasers at DAMOP 2012

Lasers are a vital research component in any number of branches of physics. From quantum physics’ quest to better understand and utilize entanglement to the creation of Bose-Einstein Condensate, from spectroscopy to laser cooling, the applications for lasers in physics are legion and ever growing. If you are doing physics research in most any field you will likely have an experimental application for lasers, but in no field is this truer than in atomic physics.

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Precision DBR Lasers -- Products, not "Pearls"

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

Back of Photodigm business card

From the Photodigm mission statement:

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Applications of Diffraction Limited Single Frequency DBR Lasers

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

Exploded pie 1 resized 600

 In its January 2011 review and forecast of the laser industry, Laser Focus World projected worldwide commercial laser revenues of $7.05 billion, of which about $3.3 billion are laser diodes.  The article goes on to provide an extensive discussion into where and how these lasers are used.  By comparing the forecasts for 2011 with those of preceding years, one is able to gain a perspective of larger trends and external factors affecting the laser business.

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Optical Feedback in Laser Packages

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

Our customers specify Photodigm precision lasers for many reasons, including their narrow linewidth, tunability, spectroscopy-certified frequency, stability, and pulsing characteristics, among others.  To meet the requirements of our customers, Photodigm offers our lasers in several package types, including free space and fiber-coupled designs.  The optimal package depends on how it is used.

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Tunable Laser Diode Absorption Spectroscopy (TLDAS) with DBR Lasers

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

DBR laser tuning curve


One of the main applications of Photodigm DBR lasers is absorption spectroscopy.  In this application, the laser is tuned by varying either current or temperature to sweep the narrow bandwidth output across an absorption line of a species of interest.  Tunable laser diode absorption spectroscopy (TLDAS) can be used to establish a precise frequency reference when the laser output is locked to an atomic transition.  Because these electronic transitions are sensitive to minute perturbations in their physical environment, these frequency references can be used as the basis for atomic clocks, gyros, magnetometers, and gravimeters. TLDAS can also be used to monitor changes in concentration of absorption species, such as O2 or I2

Photodigm DBR lasers are precisely tunable by varying either current or temperature.  Tuning coefficients are approximately 0.06 nm/C  (25GHz/ deg C) by temperature or  0.003 nm/mA (1 GHz/mA) by current.  With a linewidth of a MHz or less,  and a side mode suppression of greater than 30 dB, the Photodigm DBR laser is able to effectively probe a variety of atomic and molecular species. 


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Monolithic DBR Laser Diodes and Semiconductor Economics

  
  

Photodigm Precision Laser Blog:  Applications and Tips

 

Laser products follow a remarkably consistent trajectory.  They start out as large research systems with substantial functionality and flexibility.  They fill the optical table.  These include Ti:sapphire lasers, Ar-ion lasers, YAG lasers, and CO2 lasers. They also include hybrid semiconductor designs, such as external cavity lasers (ECLs) and volume Bragg lasers (VBGs).  As specific applications are developed, specific functionality becomes more important as the researcher optimizes the experiment.  As engineers develop products from these experiments, the requirements expand to include ruggedness and cost.  The laser component may start out as a large system, but it inevitably ends up as a high volume semiconductor.  Examples include optical storage lasers (CDs and DVDs) and telecom lasers.  As volumes go up semiconductor economics enters in, costs drop, and high volume products are enabled.  

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