Sinusoidal frequency modulation on laser diode for frequency stabilization and displacement measurement

Vu, Thanh Tung; Maeda, Yoshitaka; Aketagawa, Masato

doi:10.1016/j.measurement.2015.12.021

Cited by 11 publications

(12 citation statements)

References 13 publications

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“…The phase shift deduced from the displacement of the target mirror was measured using the first and second harmonics of the interference signal. In our previous work, there was some noise that could be seen from the harmonic signals [13,14]; hence, the measurement accuracy was reduced. In this experiment, the digital LIA (HF2LI, Zurich Instruments, Zurich, Switzerland) was employed to detect the first and second harmonics (Figure 7a).…”

Section: Frequency Stabilized For Ld At 1 Mhz Modulation Frequencymentioning

confidence: 99%

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A Displacement Measuring Interferometer Based on a Frequency-Locked Laser Diode with High Modulation Frequency

Hoang

et al. 2020

Applied Sciences

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Laser interferometers can achieve a nanometer-order uncertainty of measurements when their frequencies are locked to the reference frequencies of the atom or molecule transitions. There are three types of displacement-measuring interferometers: homodyne, heterodyne, and frequency modulation (FM) interferometers. Among these types of interferometer, the FM interferometer has many advantageous features. The interference signal is a series of time-dependent harmonics of modulation frequency, so the phase shift can be detected accurately using the synchronous detection method. Moreover, the FM interferometer is the most suitable for combination with a frequency-locked laser because both require frequency modulation. In previous research, low modulation frequencies at some tens of kHz have been used to lock the frequency of laser diodes (LDs). The low modulation frequency for the laser source means that the maximum measurement speed of the FM interferometers is limited. This paper proposes a novel contribution regarding the application of a high-frequency modulation for an LD to improve both the frequency stability of the laser source and the measurement speed of the FM interferometer. The frequency of the LD was locked to an I2 hyperfine component at 1 MHz modulation frequency. A high bandwidth lock-in amplifier was utilized to detect the saturated absorption signals of the I2 hyperfine structure and induce the signal to lock the frequency of the LD. The locked LD was then used for an FM displacement measuring interferometer. Moreover, a suitable modulation amplitude that affected the signal-to-noise ratio of both the I2 absorption signal and the harmonic intensity of the interference signal was determined. In order to verify the measurement resolution of the proposed interferometer, the displacement induced by a piezo electric actuator was concurrently measured by the interferometer and a capacitive sensor. The difference of the displacement results was less than 20 nm. To evaluate the measurement speed, the interferometer was used to measure the axial error of a high-speed spindle at 500 rpm. The main conclusion of this study is that a stable displacement interferometer with high accuracy and a high measurement speed can be achieved using an LD frequency locked to an I2 hyperfine transition at a high modulation frequency.

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Section: Frequency Stabilized For Ld At 1 Mhz Modulation Frequencymentioning

confidence: 99%

“…Another drawback of the FM is that the harmonic intensities depend on the modulation index of the LD via the presence of the Bessel functions. The modulation index is a function of the modulation excursion [13,14].…”

Section: Introductionmentioning

confidence: 99%

A Displacement Measuring Interferometer Based on a Frequency-Locked Laser Diode with High Modulation Frequency

Hoang

et al. 2020

Applied Sciences

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“…For interferometers, the measurement speed or rate implies the time required to take one displacement measurement in the unit of seconds or Hz. In our previous works, a high modulation frequency of 3 MHz was successfully applied to the LD to improve the measurement speed of the frequency modulated interferometer [13,14,29]. Moreover, a high-precision phase meter was developed to measure the phase change in the interferometer [12].…”

Section: Introductionmentioning

confidence: 99%

A New Method to Verify the Measurement Speed and Accuracy of Frequency Modulated Interferometers

Tran

et al. 2021

Applied Sciences

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The measurement speed and measurement accuracy of a displacement measuring interferometer are key parameters. To verify these parameters, a fast and high-accuracy motion is required. However, the displacement induced by a mechanical actuator generates disadvantageous features, such as slow motion, hysteresis, distortion, and vibration. This paper proposes a new method for a nonmechanical high-speed motion using an electro-optic modulator (EOM). The method is based on the principle that all displacement measuring interferometers measure the phase change to calculate the displacement. This means that the EOM can be used to accurately generate phase change rather than a mechanical actuator. The proposed method is then validated by placing the EOM into an arm of a frequency modulation interferometer. By using two lock-in amplifiers, the phase change in an EOM and, hence, the corresponding virtual displacement could be measured by the interferometer. The measurement showed that the system could achieve a displacement at 20 kHz, a speed of 6.08 mm/s, and a displacement noise level < 100 pm//√Hz above 2 kHz. The proposed virtual displacement can be applied to determine both the measurement speed and accuracy of displacement measuring interferometers, such as homodyne interferometers, heterodyne interferometers, and frequency modulated interferometers.

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“…To stabilize the LD frequency, the linear or saturated absorption of some atomic-molecular species, such as iodine molecules, rubidium atoms, and Cs atoms [1][2][3], can be utilized. Sinusoidal phase/frequency modulations (SPM/SFM) and demodulation by a lock-in amplifier (LIA) are effective techniques applied to detect the atomic or molecular absorption lines for LD frequency stabilization [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…Many researchers have developed methods of stabilizing the LD frequency to some atomic-molecular absorption lines. Vu et al performed LD frequency stabilization using both a regular LD with linear absorption [5] and an ECLD with saturated absorption [6] of iodine molecules. Some of the authors of this paper also used SPM with a fixed modulation index of 3.768 rad to detect iodine-saturated absorption and stabilize the ECLD frequency for a Mach-Zehnder displacement measuring interferometer [4].…”

Section: Introductionmentioning

confidence: 99%

Suppression of residual amplitude modulation appeared in commercial electro-optic modulator to improve iodine-frequency-stabilized laser diode using frequency modulation spectroscopy

Duong

Nguyen

et al. 2018

J. Eur. Opt. Soc.-Rapid Publ.

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Background: This paper shows how to suppress residual amplitude modulation (RAM) appeared in a commercial electro-optic modulator (EOM) to improve an iodine-frequency-stabilized laser diode (LD) using frequency modulation spectroscopy (FMS). Since the RAM of an EOM is affected by the temperature of the EOM, the DC-offset applied to the EOM and the polarization of the incident beam, it should easily fluctuate with drifts in temperature, applied voltage, and polarization. The fluctuation of the RAM of the EOM, which might decrease the frequency stability of the iodine-frequency-stabilized LD, must be eliminated by some means. Methods: In this paper, we present a theoretical analysis and experimental results to express the RAM error from the EOM in a LD frequency stabilization system near 633 nm using iodine-saturated absorption. A RAM compensation system, which actuates the temperature of the EOM and the DC-offset applied to the EOM, is constructed for the commercial EOM. Results: Using the RAM compensation system, the RAM is reduced to 10 − 4 order, and frequency stability of 3.67 × 10 − 11 for 1000 s is achieved for the LD. Conclusions: The proposed method can be applied for normal frequency stabilizing LDs, which use a commercial EOM and a low modulation index with FMS.

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Sinusoidal frequency modulation on laser diode for frequency stabilization and displacement measurement

Cited by 11 publications

References 13 publications

A Displacement Measuring Interferometer Based on a Frequency-Locked Laser Diode with High Modulation Frequency

A Displacement Measuring Interferometer Based on a Frequency-Locked Laser Diode with High Modulation Frequency

A New Method to Verify the Measurement Speed and Accuracy of Frequency Modulated Interferometers

Suppression of residual amplitude modulation appeared in commercial electro-optic modulator to improve iodine-frequency-stabilized laser diode using frequency modulation spectroscopy

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