The LDH 390 and LDH 420 are now available. The new laser heads emit around 390 nm and 420 nm with pulse widths less than 70 ps and can generate up to 5 mW average power at 40 MHz repetition rate (30 mW in the optional continuous-wave mode).
The LDH Series picosecond diode laser heads produce light pulses as short as 50 ps at repetition rates from single shot to 80 MHz (depending on the wavelength). For selected wavelengths peak powers up to 1 W can be emitted. The short pulse width perfectly matches the time resolution of mainstream detectors, yet at a price ten times lower than that of commonly used Ti:Sapphire or Argon ion lasers. A combination of interchangeable LDH Series laser heads, together with the PDL 800-B, PDL 800-D, PDL 808 "Sepia" or PDL 828 "Sepia II" driver satisfies the demand for compact and affordable excitation sources that cover a wide range of wavelengths. Previously, nanosecond flash lamps with low repetition rates or expensive and bulky Ti:Sapphire lasers were the typically employed sources. They require extensive maintenance and considerable experience to run in daily work. The LDH Series pulsed diode laser sources offer the benefits of cheap and compact integrated turn-key systems along with high repetition rates desired for fast applications like Time-Correlated Single Photon Counting (TCSPC). These features open the door for entirely new routine applications beyond the research lab, e.g. in bioanalytics, biochemistry, genetics, semiconductor characterization and quality control.
The latest generation of laser heads, the LDH-D Series, even work in pulsed and cw mode. This dual feature is only supported by the PDL 800-D or the PDL 828 "Sepia II" driver.
The system consists of a pulsed diode laser driver and interchangeable laser heads. Laser heads are available for a large number of wavelengths between 375 nm and 1990 nm. Even special frequency converted models are available that emit at 531 nm. The laser heads come with collimating optics and can be fitted with optical fibres (multi mode, single mode or polarisation maintaining single mode). A thermoelectric cooler for temperature control and output stability is available as an option or already supplied by default for certain types.
The PDL Series laser drivers feature easy-to-use controls for pulse width and laser power level either by means of a potentiometer on the front panel or by a setting in the control software (PDL 828). The pulse width can, however, not be controlled directly. Instead, the pulse width and pulse shape depend on the laser power level. For same laser heads the central emission wavelength also shifts slightly with increasing laser power.
The example on the left illustrates the dependence of the pulse width on the laser power level. A laser pulse from a typical LDH-P-C-405B is displayed operating with a repetition rate of 40 MHz with different laser intensity settings. The different curves are generated by simply changing the laser power level. "Clean" and near symmerical pulses can only be achieved close to the lasing threshold (Low Power Level) while at maximum power the pulse is broadened by shoulder and/or additional peaks (High Power Level). This behaviour thus provides maximum flexibility to adapt the laser system to the users needs and the requirements of the application.
The example on the right shows the dependence of the pulse width and the laser power level, featuring a laser pulse from a typical LDH-P-780 at a repetition rate of 40 MHz with different laser intensity settings. Again, this can be achieved with only one laser head and the tuning capability of the driver unit.