Category Archives: Technical Notes

Technical documentation and data notes for products

200W Pump Laser

Green Pump Lasers for Ultrafast Amplifiers

Ti:sapphire lasers have become prominent in the field of ultrafast oscillators and amplifiers due to their broad emission bandwidth and the ability to minimize opto-thermal effects over a wide range of operating parameters. In order to build high-average-power Ti:sapphire lasers, high-quality high-average-power green pump lasers are required.

The performance of CEO pump lasers is examined in this work, particularly the 50 mJ Patara™-HP50 YLF and 200 W Patara-HP200 YAG lasers. Analysis of pulse energy performance over repetition rate is presented, as is a summary of the beam quality, optical pulse, and long-term power stability. A discussion of reliability is also included.

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Ti:Sapphire Laser Overview

Ti:Sapphire lasers have become prominent in the field of ultrafast lasers and oscillators due to their broad emission bandwidth and the ability to minimize opto-thermal effects over a wide range of operating parameters.  This article examines the construction of a high-power Ti:Sapphire laser from the ground up.  Mode-locked lasers are discussed, as are single-pass, multi-pass, and regenerative amplifiers.  The use of pulse pickers to help generate higher pulse energies is also discussed.

In order to build high-average-power Ti:Sapphire lasers, high-quality high-average-power green pump lasers are required as pumps for the final amplification stage.  This article examines the main requirements on the pump lasers, and also discusses the relative merits of Nd:YAG and Nd:YLF systems.

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Pump Lasers for Ultrafast Amplifiers

Ti:sapphire lasers have become prominent in the field of ultrafast lasers and oscillators due to their broad emission bandwidth and the ability to minimize opto-thermal effects over a wide range of operating parameters. In order to build high-average-power Ti:sapphire lasers, high-quality high-average-power green pump lasers are required.

Cutting Edge Optronics (CEO) offers the Patara-HP family of Q-switched green lasers, which are ideally suited as pump sources for pulsed Ti:sapphire amplifiers. The performance of the Patara-HP pump lasers is examined in this work, particularly the 100W and 200W average power systems. An analysis of pulse energies at varying repetition rates, beam quality and stability, pulse-to-pulse stability, long-term power stability and beam pointing stability is presented. A discussion of laser system reliability is also included.

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HDS laser diode packaging increases power density by 2.5X

Northrop Grumman Cutting Edge Optronics has developed a laser diode array package with  minimal bar-to-bar spacing. These High Density Stack (HDS) packages allow for a power density increase on the order of ~ 2.5x when compared to industry-standard arrays.

This work contains an overview of the manufacturing process, as well as representative data for 5-, 10-, and 20-bar arrays. Near-field and power vs. current data is presented in each case. Power densities approaching 15 kW/cm² are presented. In addition, power and wavelength are presented as a function of pulse width in order to determine the acceptable operational parameters for this type of array. In the low repetition rate Nd:YAG pumping regime, all devices are shown to operate with relatively low junction temperatures.

A discussion of future work is also presented, with a focus on extending the HDS architecture to reliable operation at 300W per bar. This will enable power densities of approximately 25 kW/cm².

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Reliability of High-Power QCW Arrays

Northrop Grumman Cutting Edge Optronics has developed a family of arrays for high-power QCW operation. These arrays are built using CTE-matched heat sinks and hard solder in order to maximize the reliability of the devices.

A summary of a recent life test is presented in order to quantify the reliability of QCW arrays and associated laser gain modules. A statistical analysis of the raw lifetime data is presented in order to quantify the data in such a way that is useful for laser system designers.

The life tests demonstrate the high level of reliability of these arrays in a number of operating regimes. For single-bar arrays, a MTTF of 19.8 billion shots is predicted. For four-bar samples, a MTTF of 14.6 billion shots is predicted. In addition, data representing a large pump source is analyzed and shown to have an expected lifetime of 13.5 billion shots. This corresponds to an expected operational lifetime of greater than ten thousand hours at repetition rates less than 370 Hz.

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Laser Pulse Train Amplification with PowerPULSE Amplifiers

High peak power optical pulses are very desirable in industrial, scientific, and military applications.REA PowerPULSE However, maximum peak powers are limited by the damage threshold of the optical materials used and the amount of amplification available. While pulse-pumped amplifiers can achieve high gains, they are typically limited in total average power. Practical pulse trains contain pulses that are 10s of picoseconds in width, repeat every microsecond or faster, and have pulse bursts lasting 1-5ms or longer. Under these conditions a higher average power is needed to sustain the amplification of the pulse train.

Northrop Grumman Cutting Edge Optronics has developed a line of laser amplifiers that have the high gain of the pulse pumped amplifiers, and can maintain the amplifier gain for 1-5ms. This allows the amplification of long pulse trains using fewer devices, less gain material, and lower overall cost.

© 2011 Northrop Grumman Systems Corporation – All Rights Reserved

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kW-Class, Wavelength-Stabilized Laser Diode Arrays

Numerous laser media exist with absorption peaks that are too narrow to make use of standard laser diode pump arrays with emission widths of 2-3 nm. For these absorption peaks (such as Nd:YAG at 885nm, Nd:YVO4 at 880nm, and Yb:YAG at 969nm), laser diode pump arrays with narrower emission spectra are highly beneficial.

Northrop Grumman Cutting Edge Optronics has developed a process for building high-power laser diode arrays with narrow emission spectra by adding Volume Bragg Gratings during the packaging process. These arrays emit with a spectral width of approximately 0.5nm (FWHM), and are available with output powers ranging from tens of watts to several kilowatts. Experimental data is presented in this technical note for arrays operating at up to 100W per bar (CW).

© 2011 Northrop Grumman Systems Corporation – All Rights Reserved

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QCW Diode Array Reliability at 80x and 8xx nm

Northrop Grumman Cutting Edge Optronics (NGCEO) has recently developed high-power laser diode arrays specifically for long-life operation in quasi-CW applications. These arrays feature a new epitaxial wafer design that utilizes a large optical cavity and are packaged using AuSn solder and CTE-matched heat sinks.

This work focuses on life test matrix of multiple epitaxial structures, multiple wavelengths, and multiple drive currents.  Particular emphasis is given to the 80x and 88x wavelength bands running at 100-300 Watts per bar. Reliable operating points are identified for various applications including range finding (product lifetimes less than 1 billion shots) and industrial machining (product lifetimes greater than 20 billion shots). In addition to life test data, a summary of performance data for each epitaxial structure and each bar design is also presented.

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