Dataset for Pulsed-Laser Frequency Locking in a Compact 355-nm Direct-Detection Doppler Wind Lidar

This dataset contains the experimental data associated with the paper “Pulsed-Laser Frequency Locking for a Compact 355-nm Direct-Detection Doppler Wind Lidar”. It is used to support the performance analysis of the pulsed-laser frequency-locking technique for a compact 355 nm direct-detection Doppler wind lidar.The data were obtained from a 355 nm compact direct-detection Doppler wind lidar frequency-locking experimental system. The experimental system mainly consists of a seed-tunable 355 nm pulsed laser, a dual-channel Fabry–Perot etalon (DFP), photomultiplier tube detectors, a high-speed data acquisition module, PZT/TEC laser frequency tuning modules, and a PID feedback control program. During the experiment, the reference pulsed laser passed through the two DFP channels, and the transmitted signals were synchronously acquired by the two detection channels. These signals were used to calculate the frequency response function R(ν) and construct the frequency-locking feedback loop, ultimately achieving relative locking between the reference pulsed-laser frequency and the transmission spectrum of the DFP frequency discriminator.During data processing, the detector output waveforms were first synchronously recorded by the high-speed data acquisition module. The pulse mean values were then extracted as the transmitted intensities of the two channels, and the frequency response function R(ν) was calculated from the difference and sum of the two-channel intensities. In the frequency stability analysis, part of the frequency data was processed using a 1 s or 15 s moving average according to the actual lidar acquisition characteristics, in order to characterize the effective frequency deviation under practical detection conditions. The Allan deviation was calculated from the original closed-loop frequency data. The units of the relevant physical quantities include MHz, GHz, V, s, min, and °C, and the specific units are indicated in the corresponding data files or figure labels.Data File DescriptionsData File 1: DFP Temperature Response Test DataThis file contains the transmission spectrum data and frequency data of channel 1 of the dual-channel Fabry–Perot etalon (DFP) under different temperature conditions, corresponding to Fig. 6 in the paper. The experimental temperature range was 22–26 °C, and the data were used to evaluate the effect of temperature variation on the position of the DFP transmission spectrum.The file mainly includes two parts of data. The first part is the frequency-scanned transmittance data under 22–26 °C, namely the single-channel transmission spectra of DFP channel 1 measured at different temperatures. The second part is the frequency-scanning variation data recorded under 22–26 °C, which was used to analyze the frequency drift characteristics of the DFP transmission peak with temperature. The columns of data correspond to each other and can be used to reproduce the transmission spectrum curves at different temperatures in Fig. 6(a), as well as the linear fitting results of peak frequency versus temperature in Fig. 6(b).This dataset shows that the DFP transmission spectrum undergoes an approximately overall frequency shift as the temperature increases, while the spectral shape remains essentially unchanged. The relevant variable units include temperature (°C), relative frequency (GHz), and transmittance. The peak-frequency data can be used to calculate the temperature-induced frequency drift coefficient and support the analysis of DFP temperature sensitivity and frequency-locking reference stability in the paper.Data File 2: DFP Frequency-Scanning DataThis data file corresponds to Fig. 7 in the paper. It is mainly used to obtain the DFP dual-channel transmission spectra and the frequency-locking reference curve R(ν), and to evaluate the linear operating range of the frequency-locking reference curve.This data file consists of two sub-files. The first part is the DFP dual-channel transmittance frequency-scanning data, which contains the transmittance variations of DFP channel 1 and channel 2 during the frequency-scanning process. The second part is the Frequency_355_GHz_data frequency-scanning data, which records the corresponding relative frequency variation of the 355 nm laser during the scanning process.The two parts of data were acquired synchronously during the experiment. However, due to differences in the testing equipment and sampling methods used, the numbers of data points in the transmittance data and frequency data are not completely identical. During data processing, linear interpolation is required to match the frequency data with the transmittance data, so that the DFP channel 1 transmittance, DFP channel 2 transmittance, and normalized frequency response function R(ν) can be obtained under the same relative frequency coordinate. Here, R(ν) is calculated from the difference and sum of the two-channel transmitted signals and is used to construct the frequency-locking reference curve.Data File 3: Laser Frequency-Tuning Data under PZT Driving ModeThis data file corresponds to Fig. 8 in the paper and is mainly used to characterize the frequency tuning characteristics of the laser under PZT driving mode. The file contains PZT control voltage data and laser frequency monitoring data. The two types of data were synchronously recorded during the experiment, and the data points correspond one-to-one.During the experiment, the seed-laser frequency was tuned by changing the PZT control voltage, while the corresponding pulsed-laser frequency variation was recorded. This data can be used to analyze the response relationship between PZT control voltage and laser frequency, and to calculate the PZT tuning sensitivity and effective tuning range.Data File 4: First-Generation Frequency-Locking Scheme DataThis data file corresponds to Fig. 9 in the paper and is mainly used to show the frequency-locking process and control effect of the system under the first-generation frequency-locking control scheme. The file contains R data and time t data. The two types of data were synchronously recorded during the experiment, and the data points correspond one-to-one.Here, the t data represent the time information during the experiment. The R data are the frequency response function values calculated from the DFP dual-channel transmitted signals and can be used to characterize the deviation of the laser frequency relative to the locking reference point. According to the linear calibration relationship of the DFP frequency response curve, the R value and the frequency deviation satisfy a linear relationship, with a conversion coefficient of approximately 0.0006 MHz⁻¹, namely ΔR ≈ 0.0006 × Δf_MHz. Therefore, the frequency deviation can be approximately expressed as Δf_MHz ≈ ΔR / 0.0006.This data can be used to reproduce the frequency-locking results under the first-generation control strategy in Fig. 9, including the PZT control output variation and the corresponding laser frequency variation. The result is used to illustrate that although the first-generation scheme can achieve basic relative locking, during long-term operation or under accumulated environmental disturbances, the PZT output may gradually approach the tuning limit, and brief loss of lock and relocking may occur during switching between PZT and TEC control.Data File 5: Second-Generation Dual-Loop Experimental DataComparison between Free-Running and Locked StatesThis data file corresponds to Fig. 10 in the paper and is mainly used to compare the frequency drift characteristics of the laser under the unlocked free-running state and the second-generation cascaded dual-loop frequency-locked state. This data is used to evaluate the suppression effect of the second-generation PZT/TEC cascaded dual-loop control strategy on long-term laser frequency drift.This data file contains four data packages:(1) Original R DataThis data is the original frequency response function R data recorded when the laser was in the locked state. The R value was calculated from the DFP dual-channel transmitted signals and can be used to characterize the deviation of the laser frequency relative to the locking reference point. According to the calibrated linear relationship, the R data can be further converted into frequency deviation.(2) Total Two-Hour Locked Data_1s_movemeanThis data was obtained by applying a 1 s moving average time window to the original frequency data under the locked state. The 1 s moving average is used to simulate the multi-pulse averaging characteristics in the actual lidar data acquisition process, thereby more reasonably characterizing the effective frequency deviation under practical detection conditions.(3) One-Hour Free-Running Frequency DataThis data is the frequency monitoring data of the laser during 1 h of free-running operation without frequency locking. It is used to characterize the natural frequency drift and low-frequency fluctuation characteristics of the laser under the unlocked state.(4) Extracted Last One-Hour Locked DataThis data was extracted from the last 1 h of the “Total Two-Hour Locked Data_1s_movemean” and is used for direct comparison with the 1 h free-running frequency data. This data reflects the ability of the second-generation cascaded dual-loop control strategy to maintain laser frequency stability after long-term operation.During data processing, the original R data under the locked state were first converted into frequency deviation according to the linear calibration relationship of the DFP frequency response curve, and then the frequency data were processed using a 1 s moving average time window. The free-running data and the extracted last 1 h locked data were used to plot the frequency drift comparison curves under the unlocked and locked states in Fig. 10 of the paper.Data File 6: Second-Generation Dual-Loop Experimental Data2 h, 15 s Moving AverageThis data file corresponds to Fig. 11 in the paper and is mainly used to analyze the long-term frequency stability of the second-generation PZT/TEC cascaded dual-loop frequency-locking scheme during continuous 2 h operation. This data is used to characterize the low-frequency drift characteristics and long-term stability maintenance capability of the laser frequency under the locked state.This data file mainly contains three parts:1. 2 h Original R DataThis data is the original frequency response function R data recorded during continuous 2 h operation of the laser under the second-generation dual-loop frequency-locked state. The R value was calculated from the DFP dual-channel transmitted signals and is used to characterize the deviation of the laser frequency relative to the locking reference point. According to the linear calibration relationship of the DFP frequency response curve, the R data can be further converted into frequency deviation.2. Two-Hour R Data_15s_movemeanThis data is the result obtained by applying a 15 s moving average time window to the 2 h original R data. The 15 s moving average is mainly used to reduce the influence of high-frequency noise and to more clearly show the low-frequency drift and long-term stability variation trends during the frequency-locking process.3. Two-Hour Converted Frequency Data_15s_movemeanThis data is the frequency deviation data obtained by further converting the 15 s moving-averaged R data, with the unit of MHz. This data is used to plot the long-term frequency stability curve in Fig. 11 of the paper and to statistically analyze the fluctuation range, mean value, and standard deviation of the laser frequency during continuous 2 h operation after locking.During data processing, the original R data under the locked state were first collected continuously for 2 h. The R data were then processed using a 15 s moving average time window. Finally, the R values were converted into laser frequency deviations according to the linear calibration relationship of the frequency response curve. This processing method helps highlight the frequency stability performance over a long time scale and corresponds to the long-time averaging acquisition characteristics of practical lidar operation.Data File 7: Second-Generation Dual-Loop Experimental DataPZT OutputThis data file corresponds to Fig. 12 in the paper and is mainly used to show the output variation of the PZT control voltage during continuous 2 h operation of the second-generation PZT/TEC cascaded dual-loop frequency-locking scheme. This data is used to evaluate whether the cascaded dual-loop control strategy can maintain the PZT output within the effective tuning range, thereby avoiding long-term accumulated drift or saturation of the PZT.This data file mainly contains two columns: PZT_all output data and t_min time data. Here, PZT_all represents the output voltage at the PZT control terminal during the frequency-locking process, with the unit of V; t_min represents the corresponding experimental time, with the unit of min. The two columns of data were synchronously recorded during the experiment, and the data points correspond one-to-one.Data File 8: Second-Generation Dual-Loop Experimental DataAllan DeviationThis data file corresponds to Fig. 13 in the paper and is mainly used to evaluate the laser frequency stability under the second-generation PZT/TEC cascaded dual-loop frequency-locking scheme. This file contains Allan deviation data calculated from the continuous 2 h closed-loop frequency-locking frequency data, and is used to characterize the stability of the locked laser frequency over different averaging time scales.The Allan deviation data were calculated from the original closed-loop frequency measurement data, rather than directly from the moving-averaged frequency data. This data can be used to plot the Allan deviation curve in Fig. 13 of the paper and to analyze the frequency stability variation of the system over short, intermediate, and long averaging time scales.