Available Photonics Experiments:

P5854 Fabry Perot resonator
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  • Two mode HeNe laser
  • Multiple beam interference
  • Finesse
  • Free spectral range
  • Visibility
  • Contrast
  • Coherence length
  • Stability criterion
  • Spectral frequency and mode analysis
  • Examples of investigations and measurements
OX Setup and alignment
The initial setup uses the pilot laser (12) which is a HeNe laser emitting two orthogonally polarised modes. The first mirror (2) of the Fabry Perot cavity is mounted into a precise adjustment holder. The second mirror is attached to the piezo element (E) which is mounted into a precise adjustment holder. Both mirrors are aligned visually to each other in such a way that interference can be observed at the exit of the cavity. The piezo is connected to its controller (H) and the modulation is switched on. The photodetector (11) is connected to the signal conditioning box which output is connected to the oscilloscope. As trigger the slope of the triangularly modulated piezo voltage is used which is displayed on the second channel of the oscilloscope. By slightly mowing the adjustment holder (15) by turning the pinion drive of it. This gives an oscilloscope trace as per figure (A). At the maximum of the upper signal the position of the adjustment holder is fixed and the Fabry Perot aligned for a clear representation as shown in figure (B). In the next step the finesse is measured (figure C) and finally the mode spectrum of the probe laser (figure D)
OX Plane mirror Fabry Perot
The aim of this experiment is to demonstrate the difference between the plane and the spherical mirror Fabry Perot. The light of the probe laser is first lead into the resonator, now equipped with plane mirrors. The adjustment procedure is the same as for the spherical Fabry Perot. It will be noticed that the adjustment is obviously more critical than in the case of a spherical Fabry Perot.
The same measurements are carried out as in the spherical FP’s. Moreover, the beam will be expanded with the telescope formed by (B) and (C) , having a lens of =-5 mm and the achromatic lens f = 20 mm. Contrary to the spherical FP’s, an increase in the finesse will be observed.
Hump Mode Finesse Mode
A. Search of confocal case B. Determine free spectral range C. Measurement of finesse D. Mode spectra of probe laser
  • P5854 Fabry Perot resonator or mode analyzer, full options consisting of:
14B-00201Achromat f=20 mm, free opening 8 mm, click 25 mm
24B-02701Laser mirror holder LSF 650 - 1/2", flat, T 4% @ 632 nm
34B-02741Laser mirror ø1/2", R=75 mm, T 4% @ 632 nm in holder
44B-02761Laser mirror ø1/2", R=100 mm, T 4% @ 632 nm, in holder
54B-02801Laser mirror with piezo element mount, flat, T 4% @ 632 nm
64B-02901Laser mirror with piezo element mount, R=75 mm, T 4% @ 632 nm
74B-03001Laser mirror with piezo element mount, R=100 mm, T 4% @ 632 nm
84B-06201Biconvex lens, f=60 mm, free opening 18 mm, click 25
9ED-00601Photodetector signal conditioning box
10ED-01701Piezo controller PC-01
11ED-02101PIN Photodetector, BPX61 with connection leads
12LS-01501HeNe Pilot laser ø30 mm
13XM-02201Optics cleaning set
14XM-03861Laser mirror adjustment holder, left LSF 1/2", carrier 30 mm
15XM-03901Piezo element with adjustment holder, pinion drive and carrier 30
16XM-04001Module B - Beam expander lens with adjustment holder
17XM-04041Module C - Telescope lens f = 150 mm in holder and mounting plate
18XM-10901Mounting plate C25 with carrier 20 mm
19XM-11002Mounting plate, including carrier 20 mm , C30
20XM-90301Profile Rail OCM 650, 500 mm with gear rack 200 mm
 Required Options:  
 TP-01001Oscilloscope 100 MHz digital, two channel