The Series 70 is a range of deep UV lasers with emission lines in the 224.3nm to 291.9nm spectral range.
Peak output powers lie in the range 100 - 600mW with average output powers in the range 15 - 70 micro Watts (wavelength dependent). The HeAg emits only at 224.3nm. The NeCu emits simultaneously at as many as 10 wavelengths from 248.6 to 274.1nm, depending on the drive current setting and or mirror combination. The current configuration is set at 248nm only.
As the drive current of the NeCu is increased, the number of simultaneous emission lines increases. In applications where only one laser line is desired or demanded, an external filter, grating or prism will be needed to isolate the desired laser line.
The laser controller allows setting of drive current, pulse width and pulse rate. The specific emission wavelengths and output power are determined by the drive current setting. As the drive current is increased, the laser lines with the lowest threshold current values lase first while the laser lines with the highest threshold current values lase last.
The pulse width and pulse frequency are set to be adjustable within fixed ranges of 30msec to 200msec and 1Hz to 10Hz, respectively. External modulation is also possible. When operated in the external modulation mode, the pulse rate is selected externally while the pulse width is selected internally. Under the replica mode, the pulse repetition rate is controlled and the pulse width is set in software. A trigger of 100ns-2µs is required.
Each laser in the range is provided with a benchtop controller that is fully compatible with single phase 240VAC mains voltage. The controller is a microprocessor-based system that allows for remote control and diagnostics via an RS232 port or with additional device USB to Serial. The laser is controlled using LabView virtual instrument software installed on a PC operating at >1.0GHz (running Microsoft XP or newer).
The laser controller incorporates an internal pulse generator. It is possible to control the laser with this internal pulse generator or with an external generator or external trigger. Under the internal mode, the pulse rate and width are selected in LabView.
The average power stability is estimated to be typically < 5%. These lasers are single longitudinal mode.
The beam quality of these lasers is excellent. They have a circular, TEM00 spatial mode beam. The polarisation of the output power is 100-1.
Dimensions are detailed on the data sheet.
The laser head has a lifetime of approximately 30-50 million pulses, but can be refilled. The typical tube lifetime is around 200 million pulses. Average input power limits are set for the laser controller to protect the laser head from accidental damage. The laser head lifetime depends inversely on laser input power (a function of pulse current, width and rep rate). Therefore laser controllers are shipped with a maximum setting of 40amps, 10 Hz and 100µs for the NeCu laser and you should not exceed 20Amps, 10Hz and 200µs in the HeAg laser.
Direct deep UV emission from a unique transverse, hollow cathode discharge metal ion laser technology requires no warm-up time and allows operation of the laser in any orientation. Unlike other metal vapour lasers, the metallic active gain material is sputtered rather than being evaporated into the optical gain region of the laser tube. The rise time of the metal vapour pressure is typically about 8-15 microseconds after the initiation of a "pulse". Therefore, every pulse is similar to turning the laser on from a cold start.
This is possible because of the high energy of electrons and ions in the hollow cathode discharge. Traditional metal vapour lasers use a positive column discharge in which the electron and ion energies are much lower and the metal vapour pressure is produced by heating a reservoir of the active metal. This process requires very long warm-up times since much of the structure of the laser tube needs to be brought up to relatively high temperatures compared to ambient. The unique design and method of operation of the series 70 lasers allow for long field lifetimes since the laser need only be turned on when it is being actively used.
Another feature of this hollow cathode metal vapour laser technology is that the laser tube can be operated at very cold ambient conditions since the metal vapour pressure is not generated by macroscopic thermal heating. Instead the metal vapour pressure is generated by electron and ion energy which is typically over 200 volts and very insensitive to ambient temperature.
These lasers have the potential to operate quite well at temperatures of several hundred degrees Celsius below zero, as long as the buffer gas doesn't condense. The laser head contains an all metal/ceramic laser tube with internal mirrors, similar to a HeNe laser. The seamless INVAR laser tube body provides the hermetic chamber as well as the optical resonator. The laser beam is aligned coaxial with the laser head housing tube. Within the laser tube is contained the proprietary optical gain source which provides instant direct deep UV metal-ion emission upon start-up of the laser. The design incorporates several concepts for which patents have been awarded.
In addition to potentially unwanted laser lines, these lasers also emit incoherent plasma light over a wide range of wavelengths. However, this is managed most efficiently and effectively eliminated by the use of a proprietary double bounce plasma rejection system.