High-Speed, Repetitively Pulsed Ruby Laser Light Source

Description

PSI and Continuum have developed a high-repetition rate, multi-pulsed ruby laser as a light source for high-speed events. The Munitions Directorate at the Air Force Research Laboratory (AFRL/MD), Eglin AFB, FL sponsored this work through the Small Business Innovative Research (SBIR) program.

This red light laser incorporates repetitive Q-switching technology to achieve high individual pulse energies sufficient to overcome the self-luminosity of a supersonic bow shock.

Photo of Laser Illuminator

Features

• Repetition rates up to 500 kHz
• Pulse energies up to 1 J/pulse
• Pulse widths ~ 10 ns FWHM
• Pulse to pulse jitter < 1 ns
• Pulse to pulse energy stability better than 1 f-stop (factor 2)
• Macropulse duration > 150 µs (> 70 pulses at 500 kHz)

Single Micropulse Isolated from Laser Macropulse

Applications

• High-speed photography
• Ballistic impact
• Shaped charge formation
• Fluid mechanics, flow visualization/PIV
• Mechanical failure, crack propagation

This laser is fundamentally scalable. The technology innovations that result in this performance are applied to the oscillator cavity (high-speed Pockels cell) and to the oscillator output (low-speed Pockels cell). Amplification stages are then applied in series as required.

Figure 1 details the results of this laser operated with 2 amplification stages at 500 kHz. Figure 1a shows the photodetector trace of the macro-pulse acquired with an integrating photo-detector. The peak of the laser pulse then determines the pulse energy. Figure 1b expands the time scale of Figure 1a, and Figure 1c plots the reduced pulse energy as a function of pulse number in the macro-pulse. The amplification stages used in this example have nearly a X50 increase over oscillator output.

Figure 1

Pulse energy can be varied by a factor of 1000 to match the photographic energy requirements. Pulse energy scales inversely with the pulse repetition frequency and directly with the flashlamp pump energy and number of amplification stages incorporated.

Options

• Amplification Stages - Higher output energies can be achieved through the series addition of amplification stages. The multi-pulsed technology is applied to the oscillator cavity of a solid-state ruby laser. Therefore, a base-level system (i.e., the oscillator alone) provides the same characteristics as Figure 1 for lower output energies.
• Holographic Quality Light - Oscillator intracavity elements can be added to generate holographic quality light. Spatial and longitudinal mode selection elements have been demonstrated to work with this multi-pulsing technology.

Systems can be integrated with high-speed framing cameras, e.g., the Imacon 488 or the Cordin 330A, or with high-speed digital cameras, e.g., Silicon Mountain Design SMD-64k1M. PSI has the knowledge and experience to define image contrast and resolution performance as a function of laser capability and camera specifications. We can then integrate the laser and camera into a Complete, State-of-the-Art, High-Speed Photography System.

We work with Continuum using readily available parts to build a flexible, efficient laser with unique capability.

Peter E. Nebolsine Physical Sciences Inc. 20 New England Business Center Andover, MA 01810-1077 Telephone: (978) 689-0003 Fax: (978) 689-3232 nebolsine@psicorp.com