29 Jun 2007 Industrial-grade Nd:YAG lasers with emission wavelength at 532 nm, both lamp-pumped and diode-pumped, are well suited to pump Ti:Sapphire. These highly reliable and cost-effective lasers will produce pulse energies up to 20 mJ at 1 kHz and 13 mJ at 10 kHz. Lee Laser manufactures eight laser models with average output power from 25 Watts to 135 Watts.
For users with high pulse energy or ultra-high pulse frequency requirements, Lee Laser can combine two lasers on a single platform to achieve 40 mJ at 1 kHz. Other possible performance capabilities are: 27 mJ at 10 kHz (270 Watts average power), 3.6 mJ at 50 kHz and 1.8 mJ at 100 kHz (180 Watts average power).
The photo shows the 100-Watt diode-pumped Model LDP-200MQG.
Benefits of Intra-Cavity SHG
Lee Laser uses an intracavity second harmonic generator (SHG) within the optical resonator. The laser output coupler (mirror) is 100% reflective at 1064 nm, so that all of the power at this wavelength remains within the resonator. The output coupler also is maximum transmissive at 532 nm, so that this wavelength which is generated within the SHG crystal can be emitted from the laser. Therefore, the output coupler serves also as a wavelength separator.
It is typical for these intracavity frequency-doubled lasers to achieve their maximum average output power level at or near 10 kHz pulse rate. Therefore, it is at 10 kHz that the output power of these lasers is rated. Lesser output power levels are produced at pulse rates below and above 10 kHz.
The high level of peak power density that is needed to achieve good wavelength conversion from 1064 nm to 532 nm is provided by the high circulating power of the 1064-nm beam inside the laser optical resonator. Because the 1064-nm beam is not focused into the SHG crystal, the lifetime of the crystal is greatly extended.
This design provides a variety of other useful benefits to the user:
1. greater conversion efficiency from 1064 nm to 532 nm, up to 85 %
2. superior Q-switched pulse stability
3. permissible operation at much higher Q-switch frequencies because of better pulse stability
The design features that contribute to the superior performance stability in the Q-switched mode can cause unstable output when the lasers are operated in the CW (continuous) mode. For some applications that seem to require CW-mode operation, satisfactory results also may be achieved by operation in high-frequency (> 40 kHz) pulsed mode.
LBO SHG Crystal
Lee Laser uses LBO (lithium triborate) as its choice of harmonic generator crystal. LBO is as much as seven (7) times more durable than KTP (potassium titanyl phosphate) against internal, bulk damage from laser beam propagation. The crystal is housed inside a temperature controlled oven that maintains a temperature within + / - 0.1° C. Precise temperature control of the LBO crystal is vital to maintain a stable level of output beam power.
LBO is subject to thermal shock during high excursions of temperature change. Therefore, Lee Laser maintains the LBO crystals at a comfortable room temperature near 25°C. In the event of an electrical power failure, there is no risk of crystal damage.
SHG Crystal Protection from Laser Damage
To provide maximum protection against optical damage, Lee Laser utilizes only the most durable optical components that are commercially available. We avoid inferior optics that now are available in large quantities at very low prices, but which we know will not provide long-term reliable performance.
A special design feature of all Lee Laser Q-switched products helps to protect the SHG crystal from laser beam damage. Pulse Quench is a technique used by Lee Laser to suppress the high pulse energy and peak pulse power that is characteristic of the first pulse in a gated series of Q-switch. For frequency-doubled lasers, the giant first pulse can cause premature damage to the SHG crystal. The suppression of this first pulse by Pulse Quench greatly extends the useful lifetime of the SHG crystal.
www.leelaser.com |
