Nanosecond Pulse Shaping
Diode Laser with Programmable Pulse Shape
- Center wavelength: 1030 nm, 1064 nm, 1950 nm, others on request
- Pulse width between 1 and 330 ns with programmable pulse shape
- Repetition rate up to 1 MHz
- External trigger input
- Various operation modes: bursts, sequences, burst sequences
- Synchronization output
The PPL 400 is a stand-alone, computer controlled laser system for the generation of nanosecond pulses with programmable pulse shapes. It is connected to the host computer via a standard USB connection. It is build from four modules: a mainframe with a power supply, an oscillator module, one or two dual channel waveform generation modules and a voltage controlled laser module with polarization maintaining fiber output.
Graphical User Interface (GUI) for waveform programming
The PPL 400 can be programmed through an easy to use Windows control software. The software provides a graphical preview of the output of all waveform generators as well as the combined signal that drives the laser diode and thus corresponds to the optical pulse's temporal modulation. Last settings are saved inside the PPL 400 to allow stand-alone operation.
Programmable waveform generators
The central part of the laser system are up to 4 individual programmable waveform generators (SWM 828). Each generator outputs a combination of a flat top square pulse and a sawtooth with adjustable amplitude and slew rate. There are six variable parameters for the generated waveform:
- the time base (33 ns, 100 ns or 330 ns)
- the start time and the stop time of the pulse within the chosen time base
- the amplitude of the flat top square pulse
- the start time and ramp slew of the sawtooth within the chosen time base
The combination of these parameters allows generation of a large variety of pulse shapes, from the very basic flat top square pulse to highly sophisticated multipeak patterns. The outputs from all waveform generators are combined and connected to one input of the voltage controlled laser module. The optical output power of the laser is fully voltage controlled which allows a much better extinction ratio than electrooptically modulated sources.
The SWM 828 also features a “status control” sync output which can be connected to, e.g., an amplifier system, in order to indicate proper operation. The SWM 828 can work at any repetition rate up to 1 MHz (depending on selected time base).
Voltage controlled laser module
The voltage controlled laser module (VCL 828) is used to generate the laser emission based on the driving signals from the SWM 828 module. The output from one or two SWM 828 modules is internally combined and used to directly control the output power of the laser emission, which is highly linear with respect to the input voltage within a certain range. The laser has a lasing threshold of typically 1 mW and a maximum output power of typically 100 mW. Within this range the laser power corresponds to the control voltage between 10 mV and 1 V. At 0 V input voltage the laser is completely switched off and thus provides a very high extinction ratio between the pulses.
The oscillator module of the PPL 400 is identical to the oscillator module of the PDL 828 “Sepia II”. It has eight (individual) trigger outputs (channels) that can be addressed individually. For the PPL 400, only two channels of the SOM 828 are used for providing trigger signals to the waveform generators. The six other channels are thus free and can for example be used to define pauses between two bursts.
Repetition rates up to 30 MHz
The oscillator module provides a wide range of internal, user selectable repetition rates between 196 kHz and 80 MHz. It can also be triggered using external signals at any repetition rate between single shot and 80 MHz. The highest truly usable repetition rate for the SOM 828 within a PPL 400 device is, however, defined by the chosen time base on the waveform generation module and therefore limited to 30 MHz. At higher repetition rates, the pulses are no longer separated and the laser will switch to continuous wave operation.
Bursts up to 16.7 million pulses
The oscillator module allows to output any number of pulses between 1 and 16.772.215 (16.7 million) to one channel before the next channel becomes active (“bursts”). The output of each channel can be enabled or disabled, which is useful to insert time gaps between two bursts.
Each pulse, that is output at any of the eight channels, can be accompanied by a synchronization signal at the sync out connector of the oscillator module. This synchronization signal can be used to ,e.g., indicate proper operation to an amplifier system.
|Voltage controlled laser module (VCL 828)|
|Inputs||two analog inputs for output from SWM 828, max. superimposed analog voltage: 1 V for full optical power|
|Center wavelength||1030 nm, 1064 nm, 1950 nm, others on request|
|Spectral width||< 1 nm, wavelength dependent|
|Output connector||FC/APC fiber connector|
|Output power||50 mW after single mode fiber|
|Output stability||3% rms|
|Waveform generation module (SWM 828)|
|Input||1 external trigger (NIM) from the SOM 828|
|Outputs||analog voltage 0 to 1 V (waveform defined by software settings), status control synchronization output|
|Number of waveform generators||up to 4|
|Time base length||33 ns, 100 ns or 330 ns|
|Square pulse amplitude||freely selectable from 0 to 1 V|
|Square pulse start and stop time||freely selectable within chosen time base|
|Sawtooth (ramp) slew rate||freely selectable from 0 to 20 V/µs|
|Sawtooth (ramp) start time||freely selectable within chosen time base|
|Continuous pulse mode||pulse repetition rate from once every minute to 1 MHz and single pulse|
|Burst pulse mode||up to 16 million pulses per burst, pulse repetition rate from 196 kHz to 1 MHz, burst repetition rate from once every minute to 500 kHz|
|Oscillator module (SOM 828)|
|Input||1 external trigger|
|Outputs||8 trigger (NIM), 1 synchronization (NIM)|
|Operation modes||rotary, programmed sequence of one channel must be completed before next channel is activated, multiple channels can be combined|
|Oscillator type||crystal locked|
|Base frequencies||80, 64, 50 MHz (selectable)|
|Repetition frequency||user selectable, derived from the selected base frequency or an external trigger source by division through any integer factor between 1 and 256|
|Timing||synchronous to repetition frequency, timing position stepwise adjustable within the limits of the repetition frequency, step size equals base oscillator period|
|Amplitude||< -800 mV into 50 Ohms (NIM)|
|External trigger input|
|Amplitude||-5 to +5 V (maximum limits)|
|Trigger level||-1 to +1 V|
|Frequency range||up to 40 MHz|
|Burst length||up to 16.7 million pulses|
|Power supply||100 to 250 VAC, 50/60 Hz, max. 250 Watts|
|Dimensions||464 × 310 × 140 mm (w × d × h)|
|Operating system||WindowsTM 7 / 8 / 8.1 / 10|
All Information given here is reliable to our best knowledge. However, no responsibility is assumed for possible inaccuracies or omissions. Specifications and external appearances are subject to change without notice.
The PPL 400 laser system can be used for various applications, where programmable nanosecond pulses are important, such as:
- Seeding of fiber or solid state amplifiers
- Thin film removal
- Surface modification