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groups:mg:laserdiode_characterisation [2018/04/04 09:24] – [Current dependency] 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 =====
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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 =====
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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 =====
  
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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 ====
-<fc #ff0000> + 
-Welcher Temperatur?</fc>+Laser driver display as reference for electrical current. Temperature stabilised to 17.5°C.
  
 {{:groups:mg:rio_planex_laserdiode_characterisation_-_wavelength_vs_current.jpg?400|}} {{:groups:mg:rio_planex_laserdiode_characterisation_-_wavelength_vs_current.jpg?400|}}
  
 ==== Power vs Current ==== ==== Power vs Current ====
 +
 +Laser driver display as reference for electrical current, post-corrected using characterisation of laserdriver. Temperature stabilised to 17.5°C.
  
 === Comparison === === Comparison ===
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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 ===== ===== Long term stability =====
-<fc #ff00ff>Bisl Theorie zu Allan-deviation</fc>+ 
 +<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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 ==== Measurement 2 ==== ==== Measurement 2 ====
  
-This measurement was done for a longer period of time than measurement 1. Current set to 123.5 mA. Meerstetter set to stabilise to 17.5°C+This measurement was done for a longer period of time than measurement 1. Current set to 123.5 mA. Meerstetter set to stabilise to 17.5°C. The power was measured directly after the isolator, meaning not using the splitter, leading to higher measured powers than in measurement 1.
  
 === Temperature stability=== === Temperature stability===
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 {{:groups:mg:rio_planex_laserdiode_characterisation_-_long_term_123-5ma_17-5c_power_02.jpg?400|}}{{:groups:mg:rio_planex_laserdiode_characterisation_-_long_term_123-5ma_17-5c_allen_deviation_power_02.jpg?400|}} {{:groups:mg:rio_planex_laserdiode_characterisation_-_long_term_123-5ma_17-5c_power_02.jpg?400|}}{{:groups:mg:rio_planex_laserdiode_characterisation_-_long_term_123-5ma_17-5c_allen_deviation_power_02.jpg?400|}}
  
-==== Results ====+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.