# Gain measurements on VCSEL material using segmented contact technique - data

This dataset is organised into 9 folders:

- FIG2_CapThicknessMirrorReflectivity

- Contains two datafiles which contain the simulated top mirror reflectivities for different cap thicknesses. "AirTopMirrorReflectivity" is with air above the cap layer, and "CrAuTopMirrorReflectivity" with a 10nm Chromium layer and a 300nm Gold layer above the cap. Column 1 gives the Cap Thickness (nm), Column 2 gives the Cavity Resonance Wavelength (nm), Column 3 gives the Top Mirror Reflectivity at the cavity resonance wavelength (dimensionless).

- FIG3_CurrentSpreading

- The tif file "0d29_S1S2_ND1d5" shows the spontaneous emission profile, in the vertical direction, that was imaged with a x4 microscope objective. The filename gives the current density (kA/cm^2), the sections that were pumped, and the total value of the neutral density filters used.

- The data file "NormalisedSpontaneousEmissionProfile" give the normalised spontaneous emission profile. along a line in the gap between section 1 and 2. Column 1 gives the position (μm) where the centre of the stripe width is at zero, column 2 gives the normalised spontaneous emission intensity (x10^-2/μm).

- FIG4_SegmentedContactPI

- Contains four datafiles with the power-current characteristics of two different segmented contact sections, one with a nominally 62nm cap thickness, and the other with a nominally 124nm cap thickness. For each device, section 2 was pumped and the light emission in the in-plane and vertical direction was measured. Column 1 gives the raw current output (mA) of the pulsed current source, column 2 the current density (kA/cm^2) after correcting for leakage currents and current spreading, column 3 gives the average optical power output (μW). The current density values in column 2 are only valid above 0.1kA/cm^2, where the diode I-V curve is close to linear.

- FIG5_GainResults

- Contains the measured gain spectra for a range of temperatures and current densities, the in-plane mode loss values, and the raw amplified spontaneous emission (ASE) data used to obtain the gain spectra. This folder contains 5 sub-folders that correspond to each temperature, and a datafile called "InplaneInternalModeLoss_Summary" with the measured in-plane mode loss. In each sub-folder, there is a datafile ("#degC_GainSummary") that contains the gain spectra and the raw ASE datafiles ("#_#_S#S#_#mA_#mA"). The ASE datafile filename gives the temperature (Celsius), current density (kA/cm^2), the sections that are pumped, and the current (mA) suppled by the current source. Note that the letter d is used instead of a decimal point.

- For "InplaneInternalModeLoss_Summary", column 1 gives the temperature, column 2-9 gives the mode loss (cm^-1) obtained from the gain spectrum at each current density. The mode loss values were obtained by averaging over a 5nm wavelength range. Column 10 gives the mean (cm*-1) of columns 2-9, and column 11 gives the standard error.

- For "#degC_GainSummary", column 1 gives the wavelength (nm) and columns 2-9 gives the gain spectra (cm^-1) for each current density.

- For "#_#_S#S#_#mA_#mA", column 1 gives the wavelength (nm) and column 2 gives the ASE intensity (counts). Below this contains the spectrometer settings that were used.

- FIG6_SPVS

-Contains 6 datafiles in total. There are 5 datafiles with a filename format "SPVS#", where the # is replaced by the temperature in Celsius, that contain the photovoltage response. The datafile "SPVS_PeakWavelengthSummary" contains the cavity resonance wavelength, determined from the photovoltage peak, at each temperature.

- For the files "SPVS#", column 1 gives the wavelength (angstroms) of the light incident on the sample, column 2 gives the photovoltage response (V), and column 3 gives the standard error (V) of the photovoltage.

- For the file "SPVS_PeakWavelengthSummary", column 1 gives the temperature (Celsius), column 2 gives photovoltage peak wavelength (nm).

- FIG7_PI

- Contains the measured threshold current density, and the Power-Current (P-I) curves of VCSEL devices used to determine the threshold current. There are 5 folders containing raw Power-Current curves of devices, where the folder name gives the temperature (Celsius) at which measurements were taken. The filename of the P-I datafiles give the device name, pulsewidth (μs), and temperature (Celsius). There is a datafile called "ThresholdCurrentSummary" which contains a summary of the threshold currents obtained from the peak in the 2nd derivative of the P-I curves after smoothing using an n-point linear fit.

- For the P-I datafiles, P-I data starts from row 20 with measurement parameters given in previous rows. Column 1 gives the injection current (mA), and column 2 gives the average power (W).

- For "ThresholdCurrentDensitySummary", column 1 gives the temperature (Celsius), columns 2 and 3 gives the threshold current (mA) with the corresponding device name given by the headers in row 1, column 4 and 5 gives the threshold current density, column 6 gives the mean threshold current density (kA/cm^2), column 7 gives the standard error (kA/cm^2), column 8 gives the error due to the oxide aperture (kA/cm^2), and column 9 gives the combined error (kA/cm^2).

- FIG8_WaveguideSimulation

Contains 3 datafiles.

- "InPlaneModeProfile" gives the mode profile of the TE-polarised index guided mode at a temperature of 30degC and a wavelength of 886.5nm. Column 1 gives the vertical position (μm), column 2 gives the refractive index profile (dimensionless), and column 3 gives the normalised square magnitude of the electric field (μm^-1)

"EffectiveIndex" gives the effective index of the TE-polarised index guided mode. Column 1 gives the wavelength (nm), Columns 2-6 give the effective index (dimensionless) for each temperature (Celsius) given in the header on row 1.

"ConfinementFactor" gives the confinement factor of the TE-polarised index guided mode. Column 1 gives the wavelength (nm), Columns 2-6 give the confinement factor (dimensionless) for each temperature (Celsius) given in the header on row 1.

- FIG9_ThresholdGain

- Contains 4 data-files.

- "2ParameterGainFit" gives the in-plane modal gain-current density fits at the cavity resonance wavelength. A function of the form g = g_0*LN(J/J_tr) was fitted to the experimental in-plane net modal gain values at the cavity resonance wavelength (obtained from SPVS). g is the in-plane net modal gain, and J is the current density. g_0 and J_tr are fit parameters. Column 1 gives the temperature (Celsius), column 2 gives the fitted g_0 (cm^-1), and column 3 gives the fitted J_tr (kA/cm^2).

- "MaterialGain" gives the threshold material gain values determined from experimental measurements. Column 1 gives the temperature (Celsius), column 2 gives the in-plane net modal gain (cm^-1) at the threshold current density for each run, determined from the fit parameters in "2ParameterGainFit", column 3 gives the threshold in-plane modal gain (cm^-1) after adding the internal mode loss values from "InplaneInternalModeLoss_Summary", column 4 gives the threshold material gain (cm^-1) from converting the in-plane modal gain value to a material gain using in-plane mode parameters from "FIG8_WaveguideSimulation". Column 5 gives the modal gain error (cm^-1) due to the error in the measured threshold current density, column 6 gives the modal gain error (cm^-1) due to a wavelength uncertainty of 2nm using dg/dlambda, column 7 gives the modal gain error (cm^-1) due to the error in the in-plane internal optical loss, column 8 gives the combined modal gain error (cm^-1), and column 9 gives the threshold material gain error (cm^-1) by converting column 8 using the in-plane mode parameters from "FIG8_WaveguideSimulation".

- "CalculatedThresholdGainLiterature" and "CalculatedThresholdGainBestFit" gives the threshold material gain determined from the lasing condition using a transfer matrix method to calculate the mirror reflectivities, with doping induced internal optical loss values from literature and best fit values respectively. Column 1 gives the temperature (Celsius), column 2 gives the cavity resonance wavelength (nm), column 3 gives the gain enhancement factor due to standing wave effects (dimensionless), column 4 gives the top mirror reflectivity (dimensionless), column 5 gives the bottom mirror reflectivity (dimensionless), column 6 gives the total thickness of the active layers, and column 7 gives the threshold material gain (cm^-1).

- FIG10_GainPeak

-Contains the measured peak gain values and gain-peak wavelengths which were determined by fitting 3rd order polynominals to the gain spectra around the gain peak. There are 5 datafiles called "GainPeak_#degC" with the temperature (Celsius) given in the filename. Column 1 gives the current density (kA/cm^2), column 2 gives the measured gain-peak wavelength (nm), column 3 gives the measured peak net modal gain (cm^-1), column 4 gives the peak material gain (cm^-1).

Research results based upon these data are published at http://doi.org/ 10.1088/1361-6463/acaf0b

## Funding

### Future Compound Semiconductor Manufacturing Hub

Engineering and Physical Sciences Research Council

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- English-Great Britain (EN-GB)