LE-1300 Iodine Raman Laser

  • Molecular Spectroscopy
  • Laser pointer like excitation
  • Molecular energy level
  • Dunham Coefficients
  • Franck Condon Principle
  • Unidirectional Ring Laser Operation
  • Optical stability range
  • Raman Gain
  • Density Matrix Formalism
  • Multi-line Laser
  • Single Line Laser
  • Single Mode Ring Laser
  • Hyper Fine Structure

LE-1300 Iodine Raman LaserLE-1300 Iodine Raman Laser

The Iodine Raman laser belongs to the class of molecular laser. However, the laser transition starts from the same level as the pump laser forming a so called Λ system. Due to this coupling a variety of coherent phenomena occur. One of it is the Raman gain which leads to an asymmetrical gain distribution favoring the direction of the pump laser. This effect causes spontaneous and unidirectional propagation inside a ring laser and has been firstly observed and explained by Wellegehausen et. al. in 1979.
So far known experiments have been carried out with expensive pump laser. The invention of inexpensive laser pointer like DPSSL emitting laser radiation at 532 nm (LD) which is ideal to excite the iodine molecule allowing new affordable exciting new experiments for education. However, the underlying generation of the green radiation is based on the frequency doubling of a diode pumped Nd:VO4 laser. Such a laser has a gain bandwidth of about 1 nm. Due to thermal drift of the cavity also the frequency doubled radiation is drifting in a range of 0.5 nm. The absorption width of the Iodine molecule is much smaller compared to the thermal drift of the excitation laser. Therefore the cavity of the “green laser” must be thermally stabilized by controlling the temperature of the pump laser with an accuracy of 0.01 °C and the injection current of 0.1 mA. In such a way it is possible to tune the pump laser to the resonance of the transition indicated by the appearance of strong fluorescence light of the excited Iodine.
The ring laser cavity of the LE-1300 Iodine Raman Laser consists of four mirrors (M1...M4) forming a so called bow-tied or folded cavity. This configuration is necessary to avoid any back reflections into the single mode pump laser (LD). The mirror M2 and M3 are curved while M1 and M2 are flat ones. The Iodine cell (IC) is placed in the center between mirrors M2 and M3.
The pump radiation passes the mirror M1 and is reflected by the mirror M4 onto the curved mirror M2. Due to the curvature of M2 the pump beam is focused into the Iodine cell. The mirror M3 makes the pump beam parallel again and reflects the beam onto M1, closing the ring.

A. Iodine Raman Laser with intra-cavity birefringent tuner
A. Iodine Raman Laser with intra-cavity birefringent tuner.
A. Iodine Raman Laser with intra-cavity birefringent tuner, PZT and Photodiode
B. Iodine Raman Laser with intra-cavity birefringent tuner (BFT), piezoelectric mirror translator (PZT) and photodetector (PD).
Energy level diagram of Iodine molecules
Energy level diagram of Iodine molecules showing the ground state X and the first excited electronically molecular state

The well known Iodine molecule provides a rich variety of transitions ranging from the green up to the near infrared spectral region. The green line of an ordinary laser pointer fits to the transition from the ground state (v''=0) into the first excited electronic state (v'=32). From here more than 72 transition exist emitting back down to the ground state.
Indeed, 30 laser lines in a range from 557.3 nm to 802.7 nm can be observed within this experiment. The range is only limited by the coating of the laser mirror.
Principle of Iodine ring laser
Principle of Iodine ring laser
The Iodine is kept in an evacuated quartz cell with glass brazed Brewster windows. The ring cavity consists of 4 mirrors M1 to M4.
LE-1300 Iodine Raman Laser, consisting of:
Item Code Qty. Description
1 DC-0040 1 Diode laser controller MK1
2 LQ-0040 1 Green (532 nm) stabilized Laser, 40 mW
3 MM-0020 1 Mounting plate C25 on carrier MG20
4 MM-0160 1 Ring laser mirror mount M1 on MG65
5 MM-0162 1 Ring laser mirror mount M2 on MG65
6 MM-0163 1 Ring laser mirror mount M3 on MG65
7 MM-0164 1 Ring laser mirror mount M4 on MG65
8 MM-0218 1 4 axes adjustment holder on 20 mm carrier
9 MP-0150 2 Optical Bench MG-65, 500 mm
10 OC-0152 1 Biconvex lens f=150 mm in C25 mount
11 OC-0460 1 Transmission grating 600 l/mm
12 OC-1110 1 Laser mirror 1/2" in 1" mount, ROC flat, HR 550-800 nm
13 OC-1114 1 Laser mirror 1/2", ROC flat, HT 532, HR 540-700 nm
14 OC-1116 2 Laser mirror 1/2, ROC 250 nm, HR 520-700 nm
15 OM-3010 1 Iodine cell on carrier
16 UM-LE13 1 Manual Iodine Raman Laser
Option (order separately)
17 CA-0200 1 Oscilloscope 100 MHz digital, two channel
18 CA-0270 1 Fiber coupled spectrometer 200 - 1200 nm, USB
19 DC-0070 1 Piezo controller 0-150V
20 MM-0504 1 Piezo transducer 10µ/150V with 24 mm collar
21 OM-0580 1 Birefringent Tuner
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 Version 2019
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