STATEMENT OF WORK -- RFQ 1-116-RBG.1232

Over the past 5 years, Langley Research Center has been developing a new
optical diagnostic method called LITA (Laser-Induced Thermal Acoustics).
The method is described in detail in Applied Optics 40,965-968(2001).
LITA can measure temperature and velocity of any gas in aerodynamic
flows during a single laser pulse with 1% accuracy and precision. LITA
writes acoustic waves into the gas, which typically last 1-10 usec
depending on gas pressure. Previously, a 5-Watt single frequency CW
probe laser was used for measurements at atmospheric pressure. This
provides 5 uJ / usec laser power. To extend LITA to supersonic
low-density flows, a probe laser is required with at least 100 times
more power ie 500 uJ / usec or 500 Watts peak power spanning 1-10
microseconds. Since velocity is determined using an optical heterodyne
approach, the probe laser must have several specific characteristics,
including single frequency, single transverse and longitudinal mode, and
temporal flatness of the pulse of +/- 2% peak to valley. To obtain these
characteristics, the Contractor shall provide a laser system designed to
pulse amplify a low power single frequency YAG seeder at 1064 nm. The
seeder laser will be provided by NASA LaRC and specifications are
provided below.

The seeder/single amplifier system described is expected to provide
aerodynamic measurements at one point in space in supersonic flows. If
preliminary experiments are successful, future requirements may warrant
extending LITA to a line technique. This will require an additional two
orders of magnitude more probe laser energy ie 50,000 uJ / usec or 50 KW
peak power spanning at least 2 microseconds. Hence, the seeder/single
amplifier system should be upgradeable in future by addition of a second
amplifier. The laser characteristics of the seeder/double amplifier
system must be the same as the single amplifier system. Separate quotes
are requested for the single amplifier and second amplifier stages.

**LaRC provided YAG seeder laser specifications**

Resonant Optics Corporation Model M-800 Single Frequency Non Planar Ring
Oscillator

laser producing at least 800 mW at 1064 nm.

Has a TEM00 spatial mode

Has a single frequency longitudinal mode

Has a linewidth \< 5KHz/msec

Has a coherence length \> 1000 m

Has a drift frequency \< 50 MHz/hour

Has amplitude noise from 10 Hz to 2 MHz \< 0.1% RMS

Has a power drift over 8 hours \< 5% peak-to-peak

Has a continuous thermal tuning Range \> 10 GHz

Has a total thermal tuning Range \> 30 GHz

Has a thermal tuning Rate \> 1 GHz/sec

Has a Piezo tuning range using +-15V of \> 30 MHz

Has a small signal Piezo Response Bandwidth \> 30 KHz

#### Has a vertical polarization of 5:1

Has a beam roundness \< 20% elliptical

Has a vertical beam waist diameter of 1/e2 of 0.35 mm

Has a horizontal beam waist diameter of 1/e2 of 0.46 mm

Has a vertical full angle beam divergence \<= 3.9 mrad

Has a horizontal full angle beam divergence \<= 3.0 mrad

Has a warmup time of 1 minute

Has an operating base temperature range from 15-35 degrees Celcius.

Has a storage temperature range from -20 to 50 degrees celcius.

Has a non-condensing relative humidity range from 10-90%.

**Has a laser head size of 13 cm wide by 10 cm high by 19 cm deep**.

Has a weight \<= 1.2 Kg.

### Seeder/Single amplifier laser system specifications, or equal, having the following minimum salient characteristics:

Laser Wavelength: 1064.2 nm

Repetition rate range: 10 Hz or 200 Hz --user selectable

Total Pulse Energy: 270. Watts at 200 Hz over 60 usec wide pulse

13\. Watts at 10 Hz over 60 usec wide pulse

Specifications for 1-10 usec part of pulse

\- Pulse Energy: \> 0.5 mJ per usec( \> 0.5 KW/pulse or 500 W peak
power) during each

microsecond of user selected pulse width.

\- Pulse to Pulse Stability: Stability will be better than +/- 2%.

\- Pulse Temporal Flatness: Temporal flatness of the pulse will be +/-
2% peak to valley.

\- Pulse width: user selectable from 1 - 10 microseconds in 1.0 usec
increments.

**-** Pulse Spatial Profile: Kurtosis coefficient \< 2:1

\- Shall have remote interlock capability

\- Beam Diameter: 6 mm

\- Beam Quality (M\^2) : 2 x 4

\- Beam Divergence (mrad): 1.35 of M\^2 (\< 3 mrad)

\- Bandwidth: Single Longitudinal Mode

\- Polarization: vertically polarized 100:1

## - Cooling: Closed Loop Recirculating Distilled Water

\- Manufacturer shall supply water chiller and all appropriate
connections

\- Operating Environment: 15-30 degrees, noncondensing

\- RS 232-485 controllable

\- Shall include Operation manual and cables

\- Shall be externally triggered by TTL pulse using a BNC connector

\- Shall be diode laser pumped

-   Laser head shall have maximum dimensions of 30 inches long x 10
    inches wide x 8

inches high

-   Laser head excluding seed laser shall weigh \< 45 pounds for
    compatibility with LaRC

wind tunnel test section high accuracy and precision scanning systems.

\- Power supply shall use 208V / single phase

-   Shall have detachable water and power umbilicals between power
    supply and laser head for easy transportation and mounting in
    windtunnels

-   Shall provide users manual

**[OPTION]{.underline}**

**[Seeder/ Double amplifier laser system specifications]{.underline}**

All specs similar to seeder/single amplifier system described above with
following additions

Second amplifier shall be seeded with 2 usec pulse sliced from single
amplifier system

Second amplifier shall increase energy of sliced pulse by factor of 100
and produce

pulse energy: \> 50 mJ per usec( \> 50 KW/pulse) during each

microsecond of user selected pulse width for at least two microseconds.