DOI: 10.5061/dryad.dz08kps95
title: Data from: Solid-state high harmonic generation in common large bandgap substrate materials

description: Solid-state high harmonic generation (sHHG) spectroscopy is an emerging
 ultrafast technique for studying key material properties such as
 electronic structure at and away from equilibrium. sHHG anisotropy
 measurements, where sHHG spectra are recorded depending on the driving
 electric field relative to the crystal lattice, have become a powerful
 tool for studying crystal symmetries. Previous works on two-dimensional
 materials and other quantum materials have often used substrate-supported
 samples, assuming that all sHHG signals originate from the sample due to
 the relatively large bandgap of the substrate. While this assumption is
 generally reasonable, we show that some sHHG emissions from commonly used
 substrates can occur at moderate intensities of the sHHG driving field. In
 addition, we show that it is essential to consider not only the sHHG yield
 from a substrate but also its angular dependence relative to the material
 of interest. Specifically, in this work, the power-dependent and
 polarization angle-resolved sHHG emissions of fused silica, calcium
 fluoride, diamond, and sapphire of two different crystalline qualities and
 orientations are compared using a mid-infrared (MIR) driving field. This
 empirical characterization aims to guide the substrate selection for sHHG
 studies of novel materials to minimize the misattribution and interference
 of substrate-related sHHG emissions, which opens the possibility to study
 a wider array of materials.
description: # Data Set: Solid-state high harmonic generation in common large bandage
 substrates This data set contains all raw data and processed data for
 plotting shown in the paper that is open access here:
 [[https://pubs.acs.org/doi/full/10.1021/acs.jpca.4c04991](https://pubs.acs.org/doi/full/10.1021/acs.jpca.4c04991)]. # Description of the data and file structure The data repository contains subfolders corresponding to each figure. Each subfolder contains data files (if data is shown in the figure). The primary parameters that are varied in a given experiment are represented in the raw-file name. The raw data files themselves are encoded in ASCII and contain two columns where the first column is the wavelength in nanometers and the second column is the number of counts. Each line represents a pixel on the spectrometer. The raw data files are otherwise unprocessed spectra as measured by the spectrometer. Processed data as plotted in the manuscript is also included with the contents described in the column headings and as specified in the below readme sections. All files and folder structure mentioned below is within a single ZIP file named **data_repository_vFF.zip**  # Specific content: *Fig1:* (a) Exemplary sHHG emission spectrum of a ZnO thin-film on sapphire taken with MIR intensity of ∼1.5 TW cm–2 under ambient conditions. Data is contained in **/Fig1/a/ZnO_lens_grating_2_integ_time_1s__3uj.txt**. The filename specifies the grating used (#2 = 300 nm blaze, 300 lines/mm), integration time in seconds, and the MIR pulse energy (3 uJ, corresponding to a peak power of ~1.5 TW/cm2). This file contains the spectrum of ZnO collected through a CaF2 lens as described in the experimental section of the manuscript. The wavelength in nanometers is in the first column and the intensity in counts is in the second column. Photon energy was calculated and used for plotting in the manuscript in lieu of the wavelength. The photon energies are included in a separate text file contained in **/Fig1/a/ZnO_photon_energy.txt**. *Fig1:* (b) Spectrum of the MIR driving field used for sHHG spectroscopy reported in this work. Data is contained in **/Fig1/b/MIRspect_2.txt**. This file contains the raw ASCII data as collected from the spectrometer with wavelength in nanometers in the first column and intensity in counts in the second column. The spectrum was plotted in the manuscript with the wavelength in micrometers (nanometers divided by 1000). *Fig2*: FT-IR and UV-Vis transmission spectra of sapphire (C-plane), fused silica, calcium fluoride (100), and diamond. FT-IR transmission spectra in the mid-infrared are plotted on the left and UV-visible transmission spectra are plotted on the left. The mid-infrared transmission spectra obtained by FT-IR for fused silica, calcium fluoride, and diamond is contained in **/Fig2/FTIR/FTIR_Fig2_FigS2_FS_CaF2_diamond.txt**. The transmission spectra for sapphire (corresponding to the C-plane sample obtained from MTI) is contained in **/Fig2/FTIR/FTIR_Fig2_FigS2_sapphire_Cplane_MTI.txt**. The first three columns in each file are wavenumbers corresponding to the native unit of the original measurement, followed by conversions to wavelength in microns and photon energy in eV, respectively. The transmission data in percent transmission (%T) are included in the following columns as labeled at the top of each column. Note that this data was also used in Fig. S2 in the Supporting Information and the data has been duplicated in the data deposition for the Supporting Information. The UV-visible transmission spectra for C-plane sapphire from MTI, fused silica, calcium fluoride, and diamond is contained in **/Fig2/UVVis/UVVis_Fig2_substrate_tranmission.txt**. The three columns correspond to the wavelength in nanometers corresponding to the native unit of the original measurement, followed by conversion to wavelength in microns and photon energy in eV, respectively. The transmission data in percent transmission (%T) are included in the following columns as labeled at the top of each column. *Fig3*: (a) sHHG spectra for the 5th harmonic (H5) of different substrates studied. Data were normalized for the plot in the manuscript based on the maximum intensity and offset for clarity. Filenames include the substrate identity, pulse energy used in uJ (where 3_5uJ = 3.5 uJ, for example), the harmonic order (H5), and the grating (#1 = 800 nm blaze, 150 lines/mm, #2 = 300 nm blaze, 300 lines/mm). Raw spectra with photon energy (eV) in the first column and intensity (cts) in the second column are included for the substrates as denoted below: Sapphire (c-plane, MTI Corp.): **/Fig3/a/cPlane_sapphire_MTI_3_5uJ_H5_gr2.txt** Calcium fluoride (CaF2): **/Fig3/a/CaF2_3_4_uJ_H5_gr1.txt** Diamond: **/Fig3/a/diamond_1_2uJ_H5_gr1.txt** Fused silica: **/Fig3/a/fused_silica_3_3uJ_H5_gr1.txt** *Fig3*: (b) sHHG spectra for the 7th harmonic (H7) of calcium fluoride and fused silica. Data were normalized for the plot in the manuscript based on the maximum intensity and offset for clarity. Filenames include the substrate identity, pulse energy used in uJ (where 3_5uJ = 3.5 uJ, for example), the harmonic order (H7), and the grating (#2 = 300 nm blaze, 300 lines/mm). Raw spectra with photon energy (eV) in the first column and intensity (cts) in the second column are included for the substrates as denoted below: Calcium fluoride (CaF2): **/Fig3/b/CaF2_3_4uJ_H7_gr2.txt** Fused silica: **/Fig3/b/fused_silica_3_5uJ_H7_gr2.txt** *Fig4*: (a) Power-dependent measurements of HHG spectra for the 5th harmonic of fused silica, calcium fluoride, and poly-diamond. Spectra at each intensity were measured 4-5 times and averaged in post processing. The 5th harmonic peak was then integrated to obtain the overall harmonic intensity used in fitting the power laws. The raw spectra are contained in the folder **/Fig4/a/substrate_ID/** where **substrate_ID** is the specific substrate (**/CaF2/**, **/fused silica/**, or **/poly-diamond/**). Specific information on the filenames for raw data is listed below: Fused Silica: **4_18_2024_fused_silica_gratingX_Y.Yuj_N.txt** CaF2: **CaF2_100_pdep_gratingX_Y.Yuj_N.txt** Polycrystalline Diamond: **4_19_2024_diamond_gratingX_Y.Yuj_N.txt** For the raw data **X** refers to the grating number used in the measurement (#1 = 800 nm blaze, 150 lines/mm, #2 = 300 nm blaze, 300 lines/mm), **Y.Y** is the pulse energy used in uJ, and **N** is the iteration number. Processed data used for fitting the power laws is included in the folder **/Fig4/a/substrate_ID/processed/** where **substrate_ID** is the specific substrate (**/CaF2/**, **/fused silica/**, or **/poly-diamond/**). Processed data filenames are of the form **substrate_H5_power_dependence.txt** where **substrate** corresponds to the substrate type (**FS** = fused silica, **CaF2** = calcium fluoride, and **diamond** = polycrystalline diamond). These text files include the columns corresponding to the pulse energy in uJ, intensity in TW/cm2, and the 5th harmonic (H5) intensity in counts per second (cps). Fitting parameters for the power laws are listed in the Supporting Information for the article. *Fig4*: (b) Power-dependent measurements of HHG spectra for the 7th harmonic of fused silica and calcium fluoride. Spectra at each intensity were measured 4-5 times and averaged in post processing. The 7th harmonic peak was then integrated to obtain the overall harmonic intensity used in fitting the power laws. The raw spectra are contained in the folder **/Fig4/b/substrate_ID/** where **substrate_ID** is the specific substrate (**/CaF2/** or **/fused silica/**). Specific information on the filenames for raw data is listed below: Fused Silica: **4_18_2024_fused_silica_gratingX_Y.Yuj_N.txt** CaF2: **CaF2_100_pdep_gratingX_Y.Yuj_N.txt** For the raw data **X** refers to the grating number used in the measurement (#1 = 800 nm blaze, 150 lines/mm, #2 = 300 nm blaze, 300 lines/mm), **Y.Y** is the pulse energy used in uJ, and **N** is the iteration number. Processed data used for fitting the power laws is included in the folder **/Fig4/b/substrate_ID/processed/** where **substrate_ID** is the specific substrate (**/CaF2/** or **/fused silica/**). Processed data filenames are of the form **substrate_H7_power_dependence.txt** where **substrate** corresponds to the substrate type (**FS** = fused silica and **CaF2** = calcium fluoride). These text files include the columns corresponding to the pulse energy in uJ, intensity in TW/cm2, and the 7th harmonic (H7) intensity in counts per second (cps). Fitting parameters for the power laws are listed in the Supporting Information for the article. *Fig5*: Power-dependent measurements of HHG spectra for the 5th harmonic of C-plane sapphire from the MTI corporation, C-plane sapphire from Advalue Technology, and A-plane sapphire from the MTI corporation. The 5th harmonic peak was then integrated to obtain the overall harmonic intensity used in fitting the power laws. The raw spectra are contained in the folder **/Fig5/X/** where **X** refers to the sapphire type (**a** = C-plane sapphire from the MTI corporation, **b** = C-plane sapphire from Advalue Technology, and **c** = A-plane sapphire from the MTI corporation). Specific information on the filenames for raw data is listed below: C-plane sapphire, MTI Corp.: **cPlane_MTI_Y_YuJ__N.txt** C-plane sapphire, AdValue Tech.: **cPlane_AVT_Y_Yuj_N.txt** A-plane sapphire, MTI Corp.: **H5_TmsY_YuJ_N.txt** For the raw data **Y_Y** is the pulse energy used in uJ (the underscore represents a decimal point), **T** is the integration time in seconds (s) or milliseconds (ms) if denoted, and **N** is the iteration number. Processed data used for fitting the power laws is included in the folder **/Fig5/X/processed/** where **X** refers to the sapphire type (**a** = C-plane sapphire from the MTI Corporation, **b** = C-plane sapphire from Advalue Technology, and **c** = A-plane sapphire from the MTI Corporation). Processed data filenames are of the form **plane_manufacturer_H5_power_dependence.txt** where **plane** corresponds to the cut of the sapphire (**Csapphire** = C-plane sapphire and **Asapphire** = A-plane sapphire) and **manufacturer** refers to the supplier (**MTI** = MTI Corporation and **AVT** = AdValue Technology). These text files include the columns corresponding to the pulse energy in uJ, intensity in TW/cm2, and the 5th harmonic (H5) intensity in counts per second (cps). Fitting parameters for the power laws are listed in the Supporting Information for the article. *Fig6*: Polarization-angle resolved measurements of the 5th harmonic and the 7th harmonic of calcium fluoride and fused silica. The raw spectra are contained in the folder **/Fig6/X/** where **X** references the figure subsection corresponding to the substrate identity (**a** = CaF2 (100) and **b** = fused silica). Each angle-resolved measurement was saved as four **.txt** files named according to the date and time they were collected (**M_D_YYYY_H_MM AM/PM**). For each date string, a measurement in the parallel polarization configuration was saved with the filename containing the string “**spectrogram_0**” and a measurement in the perpendicular polarization configuration was saved containing “**spectrogram_90**”. The “**wavelengths_nm**” string indicates that the file contains the wavelengths in units of nanometers for each spectrum (where each column is a spectrum). Files with the string “**data**” contain the corresponding intensities at each wavelength (where each column is a spectrum). The entries for files containing the string “**header**” store the starting angle and ending angle (0 to 360), the degree step width, the integration time (in units of microseconds), and the number of replicates respectively. The signal was extracted from the spectra recorded at each polarization by integrating each harmonic peak using a trapezoidal sum. Prior to being integrated the harmonic spectra were scaled by the integration time such that the intensity was in units of counts per second. The triplicate measurements were then averaged and the standard deviation was taken between the spectra and was displayed as shaded error bars. Processed data is included in the folder **/Fig6/X/processed/** where where **X** references the figure subsection corresponding to the substrate identity (**a** = CaF2 (100) and **b** = fused silica). The processed data can be found in the **.txt** files with data strings “**CaF2_processed_HX_par/perp**” and “**FS_processed_HX_par/perp**” where X is the harmonic order (5 or 7), par refers to the parallel polarization configuration, perp refers to the perpendicular polarization configuration, and CaF2 and FS indicate calcium fluoride and fused silica. Each file contains columns with the polarization angle, the integrated harmonic signal at each polarization angle, and the standard deviation at each polarization angle respectively. *Fig7*: Polarization-angle resolved measurements of the 5th harmonic of C-plane sapphire from the MTI corporation, C-plane sapphire from Advalue Technology, and A-plane sapphire from the MTI corporation. The raw spectra are contained in the folder **/Fig7/X/** where **X** references the figure subsection corresponding to the cut and supplier for the sapphire substrates (**a** = A-plane, MTI Corporation, **b** = C-plane, MTI Corporation and **c** = C-plane, AdValue Technology). Each angle-resolved measurement was saved as four **.txt** files named according to the date and time they were collected (**M_D_YYYY_H_MM AM/PM**). For each date string, a measurement in the parallel polarization configuration was saved with the filename containing the string “**spectrogram_0**” and a measurement in the perpendicular polarization configuration was saved containing “**spectrogram_90**”. The “**wavelengths_nm**” string indicates that the file contains the wavelengths in units of nanometers for each spectrum (where each column is a spectrum). Files with the string “**data**” contain the corresponding intensities at each wavelength (where each column is a spectrum). The entries for files containing the string “**header**” store the starting angle and ending angle (0 to 360), the degree step width, the integration time (in units of microseconds), and the number of replicates respectively. The signal was extracted from the spectra recorded at each polarization by integrating each harmonic peak using a trapezoidal sum. Prior to being integrated the harmonic spectra were scaled by the integration time such that the intensity was in units of counts per second. The triplicate measurements were then averaged and the standard deviation was taken between the spectra and was displayed as shaded error bars. Processed data is included in the folder **/Fig7/X/processed/** where **X** references the figure subsection corresponding to the cut and supplier for the sapphire substrates (**a** = A-plane, MTI Corporation, **b** = C-plane, MTI Corporation and **c** = C-plane, AdValue Technology). The processed data can be found in the **.txt** files with data strings “**CSapphire_processed_MTI_H5_par/perp**”, “**CSapphire_processed_AVT_H5_par/perp**”, and “**ASapphire_processed_MTI_H5_par/perp**” where H5 indicates the harmonic order, par refers to the parallel polarization configuration, perp refers to the perpendicular polarization configuration, and MTI and AVD indicate the company from which the sapphire was purchased (MTI corporation or Advalue Technology) and A or C indicate whether the sapphire was A-plane or C-plane. Each file contains columns with the polarization angle, the integrated harmonic signal at each polarization angle, and the standard deviation at each polarization angle respectively. *Fig8*: (a) Polarization-angle resolved measurements of the 5th harmonic of poly-crystalline diamond. The raw spectra are contained in the folder **/Fig8/a/**. Each angle-resolved measurement was saved as four **.txt** files named according to the date and time they were collected (**M_D_YYYY_H_MM AM/PM**). For each date string, a measurement in the parallel polarization configuration was saved with the filename containing the string “**spectrogram_0**” and a measurement in the perpendicular polarization configuration was saved containing “**spectrogram_90**”. The “**wavelengths_nm**” string indicates that the file contains the wavelengths in units of nanometers for each spectrum (where each column is a spectrum). Files with the string “**data**” contain the corresponding intensities at each wavelength (where each column is a spectrum). The entries for files containing the string “**header**” store the starting angle and ending angle (0 to 360), the degree step width, the integration time (in units of microseconds), and the number of replicates respectively. The signal was extracted from the spectra recorded at each polarization by integrating each harmonic peak using a trapezoidal sum. Prior to being integrated the harmonic spectra were scaled by the integration time such that the intensity was in units of counts per second. The triplicate measurements were then averaged and the standard deviation was taken between the spectra and was displayed as shaded error bars. Processed data is included in the folder **/Fig8/a/processed/**. The processed data can be found in the **.txt** files with data string “**Diamond_processed_H5_par/perp**” where H5 indicates the harmonic order, par refers to the parallel polarization configuration, and perp refers to the perpendicular polarization configuration. Each file contains columns with the polarization angle, the integrated harmonic signal at each polarization angle, and the standard deviation at each polarization angle respectively. *Fig. 8*: (b) The raw image collected showing polycrystalline diamond is included in **/Fig8/b/2024_04_19_diamond.jpg**. The scale bar was determined by imaging a Thorlabs R1L3S2P stage micrometer with 10um subdivisions under identical conditions. The resulting micrograph of the stage micrometer, showing the 10 um scale bars, is included in **/Fig8/b/objective_calibration_ThorlabsR1L3S2P.jpg**. # Supporting Information *Fig. S1*: Comparison of infrared and UV-visible transmission for different varieties of sapphire collected by FT-IR and UV-visible spectroscopy. The mid-infrared transmission spectra for different varieties of sapphire obtained by FT-IR is contained in **/FigS1/FTIR_FigS1_sapphire_transmission.txt**. The first three columns in each file are wavenumbers corresponding to the native unit of the original measurement, followed by conversions to wavelength in microns and photon energy in eV, respectively. The transmission data in percent transmission (%T) are included in the following columns as labeled at the top of each column. The UV-visible transmission spectra for different varieties of sapphire is contained in **/Fig2/UVVis_FigS1_sapphire_transmission.txt**. The three columns correspond to the wavelength in nanometers corresponding to the native unit of the original measurement, followed by conversion to wavelength in microns and photon energy in eV, respectively. The transmission data in percent transmission (%T) are included in the following columns as labeled at the top of each column. *Fig. S2*: Larger sized FT-IR transmission spectra of sapphire (C-plane), fused silica, calcium fluoride (100), and diamond for easier identification of spectral features. The mid-infrared transmission spectra obtained by FT-IR for fused silica, calcium fluoride, and diamond is contained in **/Fig2/FTIR/FTIR_Fig2_FigS2_FS_CaF2_diamond.txt**. The transmission spectra for sapphire (corresponding to the C-plane sample obtained from MTI) is contained in **/Fig2/FTIR/FTIR_Fig2_FigS2_sapphire_Cplane_MTI.txt**. The first three columns in each file are wavenumbers corresponding to the native unit of the original measurement, followed by conversions to wavelength in microns and photon energy in eV, respectively. The transmission data in percent transmission (%T) are included in the following columns as labeled at the top of each column. Note that this data was also used in Fig. S2 in the Supporting Information and the data has been duplicated in the data deposition for the Supporting Information. *Fig. S3*: sHHG spectra for the 5th harmonic (H5) of different varieties of sapphire substrates studied. Data were normalized for the plot in the manuscript based on the maximum intensity and offset for clarity. The data plotted is included based on the provided filenames below: Sapphire (c-plane, MTI Corp.): **/FigS3/Csapphire_MTI_norm_sHHG_spectrum.txt** Sapphire (a-plane, MTI Corp.): **/FigS3/Asapphire_MTI_norm_sHHG_spectrum.txt** Sapphire (c-plane, AdValue Tech.): **/FigS3/Csapphire_AVT_norm_sHHG_spectrum.txt** All contents of this repository are CC0 compatible.