Available Photonics Experiments:

P5855 Helium Neon Laser
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  • HeNe Energy level diagram
  • Resonator stability
  • Gaussian beams
  • Birefringent crystal
  • Line & mode selection
  • Single mode etalon
  • Examples of investigations and measurements

Helium Neon Laser Basic Set-up
An open frame experimental laser based on a He-Ne tube with two Brewster’s windows (2) is used to demonstrate the laser operation. By means of the provided power supply (1) the discharge current can be adjusted to measure its influence on the laser operation. The optical resonator or cavity is formed by two common 1/2 “ exchangeable mirrors for the visible with different radii of curvature mounted in high precision adjustment holders (3 + 4). For ease of adjustment, at the beginning a pilot Laser is attached as an alignment aid. By means of the provided crossed hair target the pilot laser is aligned to the optical axis of the set-up. The laser tube is mounted into XY-adjustments to align the tube with respect to the pilot laser. Finally the mirrors are aligned with respect to the beam of the pilot laser. A birefringent filter (15) or a Littrow prism (14) is used to select a specific wavelength. By means of an etalon (14) placed into the cavity the laser is forced to single mode operation.
A photodetector (8) and an alignment laser (6) are supplied on a 1 metre optical rail (10), along with all necessary mounts and adjusters.

XP-04.02 Set-up with a Littrow prism for line selection
By replacing the flat mirror of the cavity against the Littrow prism (13), the selection of a different wavelength becomes possible. The selection of the wavelengths is carried out by means of a dispersion prism ( Littrow set-up ) or by using a birefringent filter, known as a tuning element from Dye-lasers.
XP-04.03 Set-up with birefringent tuner for line selection
This experiment enhances the understanding of the participating atomic energy levels and renders basic knowledge with regard to crystal optics, Brewster’s angle and amplification of a lasing medium. By means of the birefringent filter, a total of five visible lines can be selected. The significant influence of the discharge current on the output power is measured and discussed emphasizing on the weak lines.
XP-04.05 Set-up with etalon for single mode operation
To obtain the purest possible spectral emission the laser should operate on a single mode only. This can be achieved by using a so called Etalon, which in fact is a piece of glass with two exact parallel faces. Based on the natural reflectivity (Fresnel laws) of the faces it forms also a cavity. Placed into the Helium Neon laser master cavity it introduces extra losses. By choosing a particular length of the etalon, the system can be adjusted by tilting the etalon to operate in single mode only.
  • P-5855 Helium Neon Laser Basic Set-Up consisting of:
    1ED-00301HeNe Laser high voltage supply and controller
    2XM-02701Main laser tube with XY-adjustment
    3XM-01301Module D Laser mirror adjustment holder left with 1/2” mount
    44B-03501Laser mirror - 1/2”, R=700 mm, HR @ 632 nm
    5XM-01401Module D Laser mirror adjustment holder right with 1/2” mount
    64B-03801Laser mirror - 1/2”, flat, HR @ 632 nm
    7XM-10901Mounting Plate, including carrier 20 mm, C 25
    8XM-00801Module G - SiPIN photodetector
    9TP-00301Digital multimeter 3 1/2 digits
    10XM-11101Adjustment holder, 4 axes, carrier 20 mm
    11LS-01701Pilot laser DIMO 532 nm
    12MC-00201Optical rail MG-65, 1000 m
    163L-02201BNC / Banana connection leads 1 m
    174B-02401Optic cleaning set
    188X-XP061Manual HeNe Laser
    • Optional modules:
    XM-0260 1 Littrow prism with adjustment holder
    14 XM-0410 1 Single mode etalon with adjustment holder
    15 XM-0420 1 Birefringent tuner (Lyot filter) with adjustment holder