Application Cases

Experiment Name: Controllable Optomechanical Coupling Experiment in the Resonant Cavity of a Chip-Level Optomechanical Sensor

Research Direction: Cavity optomechanical systems, photonic crystal technology, precision measurement, noise suppression, and Q-factor enhancement.

Experiment Purpose: This study employs a chip-level optomechanical accelerometer fabricated using Silicon-On-Insulator (SOI) technology as the optomechanical system. By adjusting the fiber coupling state to change the intracavity optical field mode volume, the controllability of optomechanical coupling strength is achieved. The experiment aims to verify the enhancement of the mechanical quality factor (Q-value) and the suppression of system noise under strong interlocking conditions. The goal is to develop a high-sensitivity optomechanical accelerometer targeting the kilohertz frequency range.

Testing Equipment:

1. Optical System:

• Laser source (operating wavelength 1510 nm)

• Fiber polarization controller (FPC)

• V-groove fiber taper (transmittance > 90%)

• Photodetector (PD)

• Electronic spectrum analyzer (ESA)

• Data acquisition card (DAQ)

2. Vacuum Environment:

• Vacuum chamber (with horizontal vibration stage)

• Vacuum gauge

• Microscope observation system

3. Core Components:

• Silicon-based two-dimensional photonic crystal resonator (dimensions 16 μm × 10 μm, lattice constant 510 nm)

• High-voltage amplifier (for driving piezoelectric ceramics to generate acceleration signals)

4. Simulation Software:

• COMSOL (for electric field distribution simulation)

5. Schematic diagram of the optomechanical coupling test experimental system is shown in Figure 1 (a), and the system physical diagram is shown in Figure 1 (b).

   Notes:

• ① Laser source

• ② Fiber jumper

• ③ Three-ring polarization controller

• ④ Vacuum fiber flange

• ⑤ Vacuum chamber

• ⑥ Photodetector

• ⑦ Spectrum analyzer

• ⑧ Vacuum pin

• ⑨ Voltage source

• ⑩ Waveform generator

• ⑪ High-voltage amplifier

• ⑫ RF jumper

• ⑬ Data acquisition unit

• ⑭ Computer

• ⑮ Microscope

• ⑯ Point light source

• ⑰ Vacuum gauge

  

  
  

Figure 1: Optomechanical Coupling Test System

Experiment Process:

1. System Setup:

• (1) Install the photonic crystal resonator inside the vacuum chamber and couple the laser using a V-groove fiber.

• (2) Use a microscope and nano-actuators to precisely control the fiber position to change the optical field mode volume.

2. Coupling Control:

• (1) Adjust the contact state between the fiber and the microcavity to induce Drude self-pulsing plasma locking.

• (2) Monitor the coexistence state of self-pulsing oscillation (1510.40–1511.06 nm) and optomechanical self-sustained oscillation (1511.06–1511.86 nm). The optical characteristics of the transition state with coexisting self-pulsing oscillation and optomechanical resonance are shown in Figure 2.

Figure 2: Optical Characteristics of the Transition State with Coexisting Self-Pulsing Oscillation and Optomechanical Resonance

3. Performance Testing:

• (1) Under strong interlocking mode, apply a 6 kHz AC acceleration excitation and record the mechanical spectral response. Figure 3 shows the optomechanical sensing response in strong interlocking mode, where the black line (Test1) represents the power spectral density of the optomechanical sensor in the static state, while the blue line (Test2) and red line (Test3) at 6 kHz represent the mechanical spectra after applying different amplitudes of 6 kHz AC acceleration.

• (2) Calculate the sensitivity through spectral analysis and compare the Q-values and noise levels under weak and strong interlocking states. After linear fitting, the sensitivity of the accelerometer at 6 kHz is found to be 126.58 mV/g as shown in Figure 4.

  
  

Figure 3: Optomechanical Sensing Response under 6 kHz Acceleration Excitation in Strong Interlocking Mode

Figure 4: Sensitivity of the Accelerometer Sensor at 6 kHz under Strong Interlocking State

Experimental Results:

1. Q-value Enhancement: The mechanical Q-value under strong interlocking conditions is approximately 10 times higher than that under weak interlocking conditions.

2. Noise Suppression: The system noise floor is reduced by 26 dB.

3. Sensitivity: The accelerometer achieves a sensitivity of 126.58 mV/g at 6 kHz.

4. Optomechanical Locking: The low-frequency (72.2 kHz) optomechanical resonance is successfully locked with self-pulsing.

Power Amplifier Recommendation: ATA-2042

Figure: ATA-2042 High-Voltage Amplifier Specification Parameters