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groups:mg:laserdiode_characterisation [2018/05/08 11:42] – rholstgroups:mg:laserdiode_characterisation [2024/03/20 09:36] (current) – Admin: Syntax-Update (Migration from deprecated "fontcolor" plugin to "color" plugin) klaus
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 This characterisation is at many points compared to a {{ :groups:mg:project_ptb-cavity:105638_test_report_rev4.1_20mw_automated.pdf |report}} by rio on the factory test of the diode. The graphs taken from the factory test report use thick blue lines, the others use fine black dots. This characterisation is at many points compared to a {{ :groups:mg:project_ptb-cavity:105638_test_report_rev4.1_20mw_automated.pdf |report}} by rio on the factory test of the diode. The graphs taken from the factory test report use thick blue lines, the others use fine black dots.
 +
 +
 ===== Characterisation overview ===== ===== Characterisation overview =====
  
-<fc #ff0000>characterisation.pdf</fc>+<color #ff0000>characterisation.pdf</color>
  
 ===== Measurement setup ===== ===== Measurement setup =====
- 
----- 
  
 The Measurement setup is as shown in the picture below: The Measurement setup is as shown in the picture below:
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 The Measurements were evaluated using mathematica: {{ :groups:mg:rio_planex_laserdiode_characterisation_-_characterisation_of_measurement_setup_-_evaluation.nb |Mathematica File}} The Measurements were evaluated using mathematica: {{ :groups:mg:rio_planex_laserdiode_characterisation_-_characterisation_of_measurement_setup_-_evaluation.nb |Mathematica File}}
  
 +----
  
 ===== Spectrum ===== ===== Spectrum =====
- 
----- 
  
 ==== Direct Comparison ==== ==== Direct Comparison ====
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 In all three spectrum measurements above, the gaussian term of the Voigt fit dominates the lorentzian term. This shows that the linewidth (FWHM) in the measurements above is mainly determined by the shift of center frequency, leading to a much higher linewidth than the lorentzian FWHM of 1.3 KHz described in the test report. In all three spectrum measurements above, the gaussian term of the Voigt fit dominates the lorentzian term. This shows that the linewidth (FWHM) in the measurements above is mainly determined by the shift of center frequency, leading to a much higher linewidth than the lorentzian FWHM of 1.3 KHz described in the test report.
-===== Temperature dependency ===== 
  
 ---- ----
 +
 +===== Temperature dependency =====
  
 Meerstetter target temperature changed stepwise, measurement when temperature stabilized to ca. ±0.5mK around target temperature. Current set to 123.5 mA. Meerstetter target temperature changed stepwise, measurement when temperature stabilized to ca. ±0.5mK around target temperature. Current set to 123.5 mA.
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 {{:groups:mg:rio_planex_laserdiode_factory_test_protocol_-_power_vs_tset.png?400|}}{{:groups:mg:rio_planex_laserdiode_characterisation_-_power_vs_temperature.jpg?400|}} {{:groups:mg:rio_planex_laserdiode_factory_test_protocol_-_power_vs_tset.png?400|}}{{:groups:mg:rio_planex_laserdiode_characterisation_-_power_vs_temperature.jpg?400|}}
- 
-===== Current dependency ===== 
  
 ---- ----
  
 +===== Current dependency =====
  
 ==== Wavelength vs Current ==== ==== Wavelength vs Current ====
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 \(P\): Optical power of the laser, \(I\): Electrical current flowing through the laser \(P\): Optical power of the laser, \(I\): Electrical current flowing through the laser
-===== Long term stability ===== 
  
 ---- ----
  
-<fc #ff00ff>Bisl Theorie zu Allan-deviation</fc>+===== Long term stability ===== 
 + 
 +<color #ff00ff>Bisl Theorie zu Allan-deviation</color> 
 + 
 +==== Allan Deviation ==== 
 + 
 +To describe the instability of the measured values, the Allan deviation/overlapping Allan Deviation is used. There is a [[https://en.wikipedia.org/wiki/Allan_variance|Wikipedia article]] which explains the Allan deviation very well.
 ==== Data logging with python ==== ==== Data logging with python ====
  
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 The allen deviation shows similar characteristics as for measurement 1. The lowest relative instability is approximately 4.5*10<sup>-4</sup> for a timescale of about 100s. The power seems to underly noise on a short timescale, dominated by a drift on the larger timescale. This drift seems to be rather random comparing the graphs plotting power vs time of measurement 1 and 2. The allen deviation shows similar characteristics as for measurement 1. The lowest relative instability is approximately 4.5*10<sup>-4</sup> for a timescale of about 100s. The power seems to underly noise on a short timescale, dominated by a drift on the larger timescale. This drift seems to be rather random comparing the graphs plotting power vs time of measurement 1 and 2.
- 
-==== Results ====