Available Photonics Experiments:

P5871 Fibre Laser
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  • EDF - Erbium doped fibre
  • WDM coupler
  • Optical pumping
  • Linear and ring fibre laser
  • Passive mode locking
  • Femto second pulses
  • Spectral condensation
  • Examples of investigations and measurements
OX Principle of operation
An Erbium doped fibre is used as active material. To form a ring laser a WDM is used to couple the pump light into the fibre and to close the ring structure. The ring is opened where a thin glass plate couples a small fraction of the clockwise (cw) and counter clockwise (ccw) laser modes. By means of a SiPIN photodetector the radiation of the pump laser of 980 nm is detected and a InGaAs photodiode is used for the laser oscillation of 1.5 µm. The pump laser is controlled by the controller ED-0020 allowing the change of the temperature, injection current and modulation frequency.
OX Linear fibre laser
One end of the Erbium doped fibre (10) is connected to the pump laser and the other one to the fibre collimator(13). The emitting radiation is reflected back into the fibre with the mirror (1). A fraction of the radiation passes the mirror and is detected by the photodiode (6). Before the laser operation at 1.5 m is studied, the lifetime of the exited state is measured.
OX Ring fibre laser
The WDM coupler as well as the output coupling assembly is placed to the rail. Due to the high gain the adjustment is not critical and laser oscillation is obtained once the fibre collimator are aligned to each other. The alignment is monitored on an oscilloscope using the signal of the photodetector.
OX Spectral condensation
The mode spacing df of a ring laser is c/2L whereby c is the speed of light inside the fibre and L the length of the ring laser. With the 16 m long fibre the beat frequency of the modes is 6.2 MHz. Extending the length by 100 m neutral fibre results in 0.8 MHz which can be observed on the oscilloscope. Reducing the spectral distance of the modes results in single mode operation due to spectral condensation.
OX Passive Mode locking
The feedback mirror (1) of the linear set-up is replaced by a semiconductor saturable absorber mirror (SESAM) as a passive mode locker. The fibre length determines the pulse repetition rate and the pulse duration which will be some hundred femtoseconds determined by the dispersion and the gain. The gain also depends on the pump power and is controlled by the injection current of the pump laser diode.
The femtosecond pulses can be measured by using the manual optical delay line (XM-1060).
  • P5871 Fibre Laser consisting of:
14B-06301Front surface mirror in click 25 mm
24G-02362Fibre Patch cable ST connector on both sides, length 0.25 m
3ED-00201Digital diode laser controller
4ED-00601Photodetector signal conditioning box
5ED-02001Photodetector Si PIN
6ED-02201Photodetector, InGaAs with connection leads
7LS-09801Diode laser module, ST fibre connector
8MC-00081Profile rail MG-65, 800 mm
9MC-03101Carrier 65 mm
10XM-08961Erbium doped fibre 8 m module, ST connectors
11XM-09001WDM coupler 980/1550 nm with ST connector on carrier
12XM-09101Fibre collimator with ST connector 1 m
13XM-09201Fibre collimator with ST connector, 15 cm
14XM-10923Mounting plate C25/40, carrier 20 mm
15XM-11401Adjustment holder 40-20, carrier 20 mm
16XM-14601Output coupling module
 Required Options:  
 TP-01001Oscilloscope 100 MHz digital, two channel
 4B-10001Passive mode locker module 1.5 �m
 4B-10021Optical isolator, 1,5 �m, SM Fiber, ST
 4G-01041SM Fibre 100 m on drum, ST connector
 XM-08901Erbium doped fibre 2 m module, ST connectors
 XM-08941Erbium doped fibre 4 m module, ST connectors
 XM-08981Erbium doped fibre 16 m module, ST connectors