Requirements and Specifications_DPSS laser.docx

TITLE: Diode-pumped frequency-doubled Nd:YVO4-laser Requesting Lab/Division/Group: PML/686/11 Requisition Number: NB686110-26-00856 Requirements and Specifications:

Item 1: Diode-pumped frequency-doubled Nd:YVO4-laser To meet the project’s measurement needs described above, it is necessary to purchase a high power, single frequency, diode-pumped frequency-doubled Nd:YVO4-laser. The item must have the following capabilities:

1. The solid-state, dual 40 Watt diode-array pumped Nd:Vanadate, intracavity doubled laser must deliver greater than 18 Watts (continuous) at 532 nm.

2. Frequency doubling must be accomplished with temperature-stabilized LBO crystal. Hermetically sealed laser head with no user-adjustable controls and fiber optic connection from supply to laser head.

3. Single longitudinal mode output required. TEMoo output beam, 2.25 mm diameter (at 1/e2) with less than 0.5 mrad divergence required. M-squared <1.1 and ellipticity <10%.

4. Pointing stability must be < 3 microrad/degree Celsius.

5. Frequency stability must be <5 MHz over 50 msec.

6. Amplitude noise must be <0.05% rms from 10 Hz to 1 GHz.

7. Power stability drift must be +/- 1% or less over a two- hour or longer period.

8. Polarization: Must have vertical orientation with >100:1 extinction ratio.

9. Warm-up time from turn on to stabilized full output or at user-specified power level should be 20 minutes or less, if laser is left in stand-by mode before turn on.

10. Power requirements: 110 VAC, 60 Hz, <20 Amp.

11. At least 1 year warranty.

12. Must be able to provide 10,000 hours of continuous use without diode bar replacement.

13. The size of the laser head should not exceed 18.3 x 5.5 x 5.5 inches to allow for space on our optical table for the Ti:Sapphire oscillator.

14. The size of the power supply should not exceed 18 x 20 x 12 inches so that it may be rack mounted or fit under our optical tables.

Justification of System Requirements:

The pump laser head must be hermetically sealed so that no dust or other contaminants can enter the cavity, and no cleaning of optics is ever required. The presence of dust in the cavity makes the frequency doubling crystal susceptible to damage as it is subject to very high power densities. In a sealed cavity, there is no risk of external contamination causing damage to the intracavity doubling crystal or other optical components.

Optics within the hermetically sealed pumping laser head must be hard fastened to the baseplate without any user-adjustable mirror mounts or alignment screws. This ensures that mechanical misalignment via mount adjustment of the laser is impossible and that the alignment of optics is never required. This approach also minimizes the optical noise of the laser output.

To ensure the lowest possible output power noise specification, the laser may use an intracavity bandwidth-limiting etalon to allow single longitudinal mode operation (<5 MHz over 50 msec). The laser should then produce amplitude noise measured at 0.05% rms or less from 10Hz to 1GHz.

Laser Diode Requirements:

As diodes age, their emission wavelength shifts. The emission wavelength of the diode bars should be automatically monitored and temperature tuned to the peak of the Vanadate crystal absorption to minimize current through the diode bars and thereby extend diode bar lifetimes. This results in less cost for diode bar replacement and reduced system down time. To ensure longevity of the dual diode bars that pump the Vanadate laser crystal, the diode bar material should have no aluminum in the active area to eliminate the main failure mechanism of diode lasers: catastrophic optical damage due to oxidation of aluminum at the diode facet. Diode bars should be run at 65% or less than their rated maximum output current to reduce damage and increase diode lifetimes.

Customer field replacement of the diode bars housed in the power supply should be connected to the optical fiber umbilical via a SMA-type connector for convenient change-outs. The bar modules should include electrostatic discharge protection. When changing the diode bars, it should not be necessary to feed the fibers in and out of the umbilical cord. Fiber efficiency should exceed 85% energy coupling.

Diode Bar aging should not exceed 0.6% current increase per 1000 hours of use. This should ensure over 20,000 hours of continuous use without diode bar replacement.

Aging of the pump laser doubling crystal can cause long term drifts in the LBO doubling efficiency. The LBO should be automatically temperature tuned to peak the system output efficiency, resulting in a lower drive current to the diode bars and longer diode lifetime. This results in less cost for diode replacement and reduced system down time.

The size of the laser head should not exceed 18.3 x 5.5 x 5.5 inches to allow for space on our optical table for the Ti:Sapphire oscillator.

The size of the power supply should not exceed 18 x 20 x 12 inches so that it may be rack mounted or fit under our optical tables. Standard 110 VAC single phase power at less than 20 Amps. There must be user-controlled adjustment (via a moveable remote control module and/or computer interface) of the power supply to vary the output power of the laser to a fixed and selected power level.

Warm-up time from turn on to stabilized full output or at user-specified power level should be 20 minutes or less, if laser is left in stand-by mode before turn on.