Benefits of Cryogenic Cooling

KMLabs uses compact He-gas cryo-cooling systems or liquid He cryorefrigerator systems.  These are compact, fully-interlocked and maintenance-free, and can be configured to minimize vibration for demanding applications such as carrier envelope phase stabilization.

Cryogenic cooling reduces the thermal lens by a factor of 250 at 100W of pump. This makes the optical alignment insensitive to the pump power, and thus allows real-time change of the repetition rate, without optical realignment.

KMLabs holds an exclusive license for the patent on cryogenic-cooling of single-stage amplifier systems (or the first stage of multi-stage systems).  Whether in a regenerative or a multi-pass amplifier, the first stage is the one that is far-and-away most sensitive to the deleterious impact of thermal lensing.  This is because of the small mode size and the large number of passes through the gain material.  Hence, although it is possible to stabilize a first stage amplifier at power levels up to ~ 3 W without cryo-cooling, the system is then restricted to operate only at a single power level (i.e. a single energy and repetition rate) making it very limited in operation.  Moreover higher order aberrations remain, significantly limiting beam quality.   Spatial filtering can restore beam quality but at the cost of laser efficiency and, therefore, of maximum operating power.   This capability underpins KMLabs unique ability to offer versatile repetition rate and power-scalable systems.

Dragon™ amplifier systems can employ a variety of Q-switched frequency doubled Nd:YLF or Nd:YAG pump lasers.  With only minor modifications, the same Dragon amplifier can be used with a whole range of these different pump lasers, accessing entirely different ranges of operation.  This gives the user the flexibility to choose the highest possible energies for some experiments, and a higher repetition rate for experiments that are data-acquisition-time limited.

Eliminating the thermal lens also greatly reduces the risk of damage during system alignment.  In non cryo-cooled systems, the thermal lens is optically compensated only at full power, and so the system must be aligned at full power because only then will the optical compensation be correct. This introduces a serious risk of component damage.