Difference-frequency generation in an AlGaAs Bragg-reflection waveguide using an on-chip electrically-pumped quantum dot laser

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DATA DESCRIPTION FOR 
"Difference-frequency generation in an AlGaAs Bragg-reflection waveguide using an on-chip electrically-pumped quantum dot laser"

Alexander Schlager
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also available as readme.txt

2021-06-16 


Table of Contents
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1) Figure 2  - Lasing Threshold
2) Figure 3  - Difference Frequency Generation
3) Table 1   - Conversion Efficiency
4) Figure A3 - Temperature Dependency
5) Table A3  - Further Conversion Efficiencies



Each filename pre-pended with the figure/table number of the main and supplementary text that it contributes to. All files relevant to each figure/table are included. All numeric data is presented in tab separated variable (in a '*.txt' file) which can be opened with standard spreadsheet or text editing programs.

Aside from the JSI ('FIG3c-JSI.txt') and the temperature dependency of the internal laser spectrum ('FIGA3a-laser-temp.txt') all the plots are directly generated with a Latex package called `pgfplots'. For the two exceptions a high resolution image ('*.png') has been generated with Wolfram Mathematica and imported via 'pgfplots'.

The code used to process this data and calculate e.g. the conversion efficiencies is not contained in this repository, but can be requested from the authors if required.


1) Figure 2 - Lasing Threshold
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'FIG2-threshold-data.txt' contains the raw data of the lasing threshold measurement. Column 1 and 2 contain the current and its standard deviation in Ampere and column 3 and 4 the optical power and its standard deviation in micro Watt after a measurement time of 30 seconds. 
  
'FIG2-inset-540mA.txt' and 'FIG2-inset-700mA.txt' contain the data representing the spectra of the internal laser below and above lasing threshold. Column 1 is the wavelength in nanometers and column 2 the signal strength in kCounts/s and MCounts/s for a current of 540mA and 700mA, respectively.


2) Figure 3 - Difference Frequency Generation
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'FIG3b-example-data.txt' contains a background subtracted dataset utilizing the internal laser and a seed wavelength of 1614nm. Column 1 is  the wavelength in nanometers and column 2 the signal strength in Counts per second (Hz). This data has been averaged for an acquisition time of 300 seconds.
  
'FIG3c-JSI.txt' contains processed data for the joint spectral intensity. The DFG peaks collected in the measurements (such as in 'FIG3b-example-data.txt') have been fitted with a Gaussian function and these functions have been utilized to generate the data in this file. This allows us to properly show the Full-Width-Half-Maximum of the measured spectrum and get rid of residual background light from e.g. the telecom seed laser near the degeneracy. 
  
This data has been corrected for the bandpass filters utilized in the experiment and the detection efficiency of our detector at different wavelengths. It has then be renormalized to ease the creation of the plot.
  
The raw data for the individual wavelength settings are not included in this repository, but can be requested from the authors if required.
  
The data for Fig. 3d) is included 3) Table 1 - Conversion Efficiency (next section).



3) Table 1 - Conversion Efficiency
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'TAB1-DFG-power-int-1626nm.txt', 'TAB1-DFG-power-ext-1619nm.txt' and 'TAB1-DFG-power-pas-1510nm.txt' include the data to get the slope for the conversion efficiency for the internal laser, the external laser and the passive sample, respectively. Column 1 and 2 describe the optical power and its standard deviation of the seed laser within the waveguide in milli Watt (for correction, see supplementary materials) for a measurement time of 30 seconds. Column 3 and 4 contain the signal strength of the DFG light in counts/s (Hz) and its poissonian standard error of mean for an acquisition time of 300 seconds (internal), 10 seconds (external) and 2 seconds (passive). 
  
To extract the signal strength, we simple take sum of the maximum of the corresponding peak in the raw data (such as in 'FIG3b-example-data.txt') and its nearest neighbors, as this corresponds to the peak width of about 1-2 nm.

The raw data are not included in this repository, but can be requested from the authors if required.


4) Figure A3 - Temperature Dependency
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'FIGA3a-laser-temp.txt' contains the spectra of the internal laser for different temperature settings as shown in the supplementary materials. Column 1 is the temperature in °C, column 2 the wavelength in nanometers and column 3 the normalized signal strength. Note, that the picture used in Fig. A3a) is only a small cutout of the spectra, but contains all the important information, as there is only background below 788nm and above 794nm. 
  
'FIGA3b-shg-type0.txt', 'FIGA3b-shg-type1.txt' and 'FIGA3b-shg-type2.txt' contain the spectral information of the type-0, type-1 and type-2 second harmonic generation process, respectively. This data has been processed already, as it contains the peak maximum position (column 3) and half-width-half-maximum (column 4) in nanometers extracted from Gaussian fits for the individual SHG spectra at different temperatures in °C (column 1) with an accuracy of 0.05°C (column 2). The maximum peak position is used to create the thick line and the half-width-half-maximum is used to create the slightly transparent bands in Fig. A3b). The raw data are not included in this repository, but can be requested from the authors if required.  
  
'FIGA3c-spectrum-693mA.txt' and 'FIGA3c-spectrum-700mA.txt' include the raw internal laser spectrum at a temperature of 3.5°C and 693mA and 700mA of current, respectively. Column 1 is the wavelength in nanometers and column 2 the normalized laser power. 
  
'FIGA3d-shg-spectrum.txt' shows the second harmonic generation spectrum of the type-2 process in our waveguide at a temperature of 3.5°C. Column 1 is the wavelength in nanometers and column 2 the normalized SHG power. This data has been generated by measuring the maximum of the SHG spectrum for different pump laser wavelengths. This way, we can extract the SHG spectrum at a much higher resolution by slowly varying the laser wavelength in steps of 0.01nm. The raw data are not included in this repository, but can be requested from the  authors if required.


5) Table A3  - Further Conversion Efficiencies
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All files starting with 'TABA3-DFG-power-*.txt' include the data to get the slope for the conversion efficiency for the internal laser, the external laser and the passive sample shown in the supplementary materials, respectively. Aside from additional wavelength settings for the telecom seed laser, the description is exactly the same as in 3) Table 1 - Conversion efficiency.