BDS-MM series picosecond diode lasers

Compared with the BDS-SM versions, the output power is considerably higher. The pulse shape remains near Gaussian up to about 15 mW at 50 MHz repetition rate, see figure right. However, the output beam is multi-mode and thus cannot be focused into a diffraction-limited spot or coupled into a single-mode fibre. If fibre coupling is desired multimode fibres of larger than 100 micrometers diameter must be used. Typical applications are NIRS and fNIRS experiments and fluorescence-lifetime spectrometers.

As with the other BDS family of lasers, all the pulse driver and control circuitry is contained in the laser head. All that is needed to operate the lasers is contained in a 40 x 40 x 120mm laser head. All that is needed to operate the lasers is a +12 V power supply and a few control signals for setting repetition rate and optical power. Pulse repetition rate in pulsed mode is 20, or 50MHz, other repetition rates are available on request or can be obtained by external triggering.
In OEM applications the laser head can be embedded as it is, with the the extarnal system providing the control signals. For stand-alone applications the LSB-C laser switch box or the LSB-C2 dual-laser switch boxes are available, see photos below. Software-generated control signals can be provides by the bh DCC-100 and DCU-400/800 detector/laser controllers.
Due to an internal power regulation loop, the BDS-MM lasers feature extraodinarily stable optical power. Intensity drift by temperature changes and intensity noise by mode fluctuations in the laser diode are almost entirely suppressed. The lasers have a fast on/off function which can be used for beam blanking in scanning applications and for laser multiplexing. The reaction time of the optical output power to the ON/OFF control is on the order of a few microseconds.

The BDS-MM lasers deliver a trigger output signal for synchronisation to bh TCSPC devices. The output amplitude is sufficient for distribution of the trigger signal to several TCSPC modules. The timing stability of the trigger pulses versus the optical pulses is better than 5 ps. Extended warm-up times are not needed. After switch-on of the power supply, the timing is stable after less than a minute warm up time. The BDS-SM lasers can also be triggered externally. However, the trigger frequency should be in the range from 10 to 50 MHz in order to keep the intensity-regulation loop in the active range.

Multi-Mode Picosecond Diode Lasers
Free Beam or Multi-Mode Fiber Output
Optical Power up to 60 mW
Pulse Width Down to 65 ps
Repetition Rate 20 MHz and 50 MHz
External Trigger via Synchronisation Input
Internal power stabilization loop
Fast ON / OFF / multiplexing capability
All electronics integrated in 40 x 40 x 120 mm case
No external driver unit required
Simple +12 V supply
Size 40 x 40 x 120 mm3, with cooling fan 40 x 70 x 120 mm3

NIRS
fNIRS