Measurement of two-photon absorption coefficient of 1030 nm ultrashort laser pulses on natural diamond color centers
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Оптика и спектроскопия |
| Authors | Gulina Y.S. |
| Institutions | P.N. Lebedev Physical Institute of the Russian Academy of Sciences |
| Citations | 3 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This study experimentally quantified the nonlinear absorption characteristics of natural diamond when irradiated by ultrashort 1030 nm laser pulses, providing critical data for laser processing applications.
- Core Achievement: The two-photon absorption (TPA) coefficient (β2) was accurately measured for 1030 nm ultrashort pulses in natural diamond.
- Quantified Value: The TPA coefficient was determined to be 4.1 ± 0.3 cm/TW.
- Dominant Mechanism: At moderate intensities (not exceeding 10 TW/cm2), the primary attenuation mechanism is confirmed to be two-photon absorption occurring at induced color centers within the diamond bulk.
- Material Context: Measurements were performed on a 1 mm thick plane-parallel natural diamond plate, focusing the beam 100 µm below the surface.
- Pulse Regime: The analysis utilized both femtosecond (0.3 ps) and picosecond (10 ps) pulses, confirming the TPA mechanism across these durations.
- Engineering Impact: This data is essential for correcting theoretical simulations of energy deposition, enabling precise control over laser structuring and micromachining of diamond dielectrics.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Material Tested | Natural Diamond | Plate | 1 mm thick, plane-parallel |
| Laser Source | Fiber Yb+3 ion laser | N/A | Satsuma (Amplitude Systemes) |
| Laser Wavelength | 1030 | nm | Near-infrared regime |
| Pulse Durations Tested | 0.3 and 10 | ps | Ultrashort pulse regime |
| Pulse Repetition Rate | 2 | kHz | Standard operating frequency |
| Pulse Energy Range | 3.2 to 546 | nJ | Range used for transmission measurements |
| Two-Photon Absorption Coefficient (β2) | 4.1 ± 0.3 | cm/TW | Measured value at 1030 nm |
| Maximum Intensity Tested | 10 | TW/cm2 | Limit before critical self-focusing (filamentation) |
| Critical Self-Focusing Power (Pcrit) | ≈ 0.4 | MW | For 0.3 ps pulses at 1030 nm |
| Numerical Aperture (NA) | 0.55 | Dimensionless | Microscope objective used for focusing |
| Objective Focal Length (f’) | 5 | mm | Focusing optics specification |
| Focal Spot Radius (w0) | 1.17 | µm | Calculated spot size (1/e energy level) |
| Focusing Depth | 100 | µm | Below the front surface of the sample |
Key Methodologies
Section titled “Key Methodologies”The two-photon absorption coefficient (β2) was determined using a nonlinear transmission measurement technique, analyzing the attenuation of focused ultrashort pulses passing through the diamond sample.
- Sample Preparation and Mounting: A 1 mm thick, double-sided polished natural diamond plate was fixed onto a three-coordinate movable platform (3D-MP).
- Laser Configuration: A 1030 nm Yb+3 fiber laser was configured to deliver linearly polarized pulses at 0.3 ps and 10 ps durations, with energies varied from 3.2 to 546 nJ.
- Focusing Geometry: Laser radiation was focused using a microscope objective (NA = 0.55, f’ = 5 mm) to a focal spot radius of 1.17 µm. The focal point was positioned 100 µm beneath the diamond surface.
- Transmission Measurement: An Ophir PD10-C energy meter was placed beneath the sample to record the total energy transmitted through the diamond plate for various input pulse intensities (I0).
- Nonlinear Analysis: The nonlinear transmission coefficient (TNL) was calculated. The absorption mechanism (n-photon) was identified by plotting the normalized transmission data against intensity:
- TPA (n=2) was confirmed by observing a linear relationship between (T0/TNL) - 1 and the input intensity I0.
- Three-photon absorption (n=3) would have required a linear relationship between (T0/TNL)2 - 1 and I02, which was found to be a poorer fit.
- Coefficient Determination: The TPA coefficient (β2) was extracted by fitting the experimental data to the theoretical nonlinear transmission formula (Equation 3), which accounts for reflection losses and absorption primarily within the focal region (twice the Rayleigh length, ZR).
Commercial Applications
Section titled “Commercial Applications”The precise control over energy deposition and understanding of nonlinear absorption mechanisms in diamond are critical for advanced manufacturing and quantum technology sectors.
- Advanced Laser Micromachining:
- Enables highly localized, non-destructive internal modification of diamond substrates for creating buried circuits or structural features.
- Crucial for optimizing parameters (pulse duration, intensity) to prevent catastrophic self-focusing or filamentation during deep drilling or cutting.
- Quantum Sensing and Computing:
- Used in the precise creation and manipulation of nitrogen-vacancy (NV) color centers in diamond, which are essential solid-state qubits and quantum sensors.
- The TPA mechanism is likely responsible for inducing these color centers at the focal point.
- High-Power Laser Optics:
- Designing diamond optical components (windows, prisms) for high-intensity, ultrashort pulse laser systems where nonlinear losses must be accurately modeled to ensure system efficiency and prevent damage.
- Integrated Photonics:
- Fabrication of buried optical waveguides and couplers within diamond, leveraging TPA to initiate localized material modification for refractive index changes.
- Thermal Management Substrates:
- Improving the reliability of diamond heat sinks and electronic substrates by understanding how intense laser processing affects the material’s structural integrity and thermal conductivity.
View Original Abstract
An experimental study of nonlinear absorption process of ultrashort laser pulses in bulk of natural diamond has been carried out. The results of experimental studies on measuring nonlinear transmission of 1 mm thick plane-parallel plate made of diamond irradiated with focused by micro lens (NA=0.55 with focal length f’=5 mm) 0.3 and 10 ps laser pulses with 1030 nm wavelength are presented. It is shown that in this sample the main attenuation mechanism of ultrashort laser pulses with 1030 nm wavelength at intensities not exceeding 10 TW/cm 2 is two-photon absorption at color centers, the absorption coefficient β 2 =4.1 ± 0.3 cm/TW is determined. Keywords: femtosecond laser pulses, nonlinear absorption, natural diamond, multiphoton absorption, color centers.