Ion-Implanted Diamond Blade Diced Ridge Waveguides in Pr -YLF—Optical Characterization and Small-Signal Gain Measurement

At a Glance

Metadata	Details
Publication Date	2025-04-30
Journal	Applied Sciences
Authors	O. Al-Taher, Kore Hasse, Sergiy Suntsov, Hiroki Tanaka, Christian Kränkel
Institutions	Helmut Schmidt University, Czech Academy of Sciences, Nuclear Physics Institute
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Ion-Implanted Diamond Blade Diced Ridge Waveguides in Pr:YLF

Executive Summary

This document analyzes the fabrication and characterization of high-performance Pr:YLF ridge waveguides, focusing on the critical role of precision diamond tooling in achieving strong light confinement and high optical gain.

Core Achievement: Successful fabrication of ridge waveguides in Pr:YLF using a two-step process: C³⁺ ion implantation for planar guiding, followed by precision diamond blade dicing for lateral confinement.
Performance Metrics: Achieved ultra-low propagation losses of 0.4 dB/cm (TM polarization), comparable to state-of-the-art fs laser-inscribed waveguides.
Optical Gain: Demonstrated significant small-signal optical gain of 6.5 dB/cm at 607 nm (orange) and 5 dB/cm at 639 nm (red) under 444 nm blue pumping.
Integrated Photonics Potential: The ridge geometry enables superior optical mode confinement and high pump/signal overlap, making these structures highly promising candidates for compact, high-power integrated visible lasers in the watt range.
Material Challenge & Opportunity: The research identified surface quality issues (striped pattern, blade roughening) resulting from the dicing process, highlighting the need for optimized, high-quality diamond tooling and dicing parameters—a direct application for 6CCVD’s high-purity diamond materials.
Spectroscopic Integrity: Ion implantation was confirmed to have no negative effect on the spectroscopic properties or lifetime (50 µs) of the Pr³⁺ upper levels.

Technical Specifications

Parameter	Value	Unit	Context
Lowest Propagation Loss (TM)	0.4	dB/cm	Measured in 22 µm wide ridge waveguide
Highest Small-Signal Gain	6.5	dB/cm	Achieved at 607 nm (Orange)
Secondary Small-Signal Gain	5	dB/cm	Achieved at 639 nm (Red)
Pump Wavelength	444	nm	Frequency-doubled laser (Blue)
Ion Implantation Species	C³⁺ (Carbon)	-	Swift-heavy ion implantation
Ion Energy	10	MeV	-
Ion Fluence Range (Dose)	2 × 10¹⁴ to 6 × 10¹⁵	ions/cm²	Used for Pr:YLF samples
Ridge Width Range	13-25	µm	Used for lateral light confinement
Ridge Height	15	µm	-
Optical Barrier Depth	6.2	µm	Located near the ion stopping range
Annealing Temperature (Max)	250	°C	Stepwise annealing to reduce defects
Fluorescence Lifetime (Waveguide)	50	µs	³P₀ level lifetime

Key Methodologies

The fabrication relies on a precise combination of ion beam modification and high-precision mechanical processing enabled by diamond tooling.

Crystal Growth & Preparation: 0.5 at.% Pr³⁺ doped YLF a-cut samples were grown using the Czochralski method and prepared for implantation.
Planar Waveguide Formation: Samples were irradiated with 10 MeV C³⁺ ions, tilted 7° from the normal, creating a refractive index barrier at approximately 6.2 µm depth.
Defect Reduction (Annealing): Samples were annealed in air up to 250 °C in 50 °C increments (30 min hold time) to reduce ion-induced electronic defects and minimize optical propagation losses.
Ridge Waveguide Fabrication (Precision Dicing): Lateral confinement was achieved by cutting ridges (13-25 µm width, 15 µm height) perpendicular to the c-axis using a Disco DAD322 precision diamond saw.
Dicing Parameters: A soft resin-bonded diamond blade (200 µm width) was used at 25,000 rpm with a slow feed speed of 0.2 mm/s to minimize chipping in the YLF crystal.
Facet Preparation: End facets were prepared using 50 µm deep “polishing cuts” with the same diamond blade to ensure efficient coupling.

6CCVD Solutions & Capabilities

The successful replication and scaling of this research—particularly the optimization of the dicing process and the subsequent integration of the high-power visible laser—requires materials and services where 6CCVD excels. The noted issues with blade roughening and surface quality (striped pattern) directly point to the need for superior diamond materials and precision finishing.

Applicable Materials

Research Application	6CCVD Material Recommendation	Rationale & Specification
Precision Dicing Tooling	Polycrystalline Diamond (PCD)	High-toughness PCD is essential for manufacturing durable, ultra-sharp dicing blades that resist roughening and maintain edge quality, crucial for minimizing the “striped pattern” observed on YLF facets. 6CCVD offers PCD plates up to 125mm.
High-Power Thermal Management	Optical Grade Single Crystal Diamond (SCD)	Integrated visible lasers operating in the watt range require extreme heat dissipation. SCD provides thermal conductivity > 2000 W/mK, ensuring stable operation and preventing thermal rollover.
Integrated Substrates	Optical Grade SCD or PCD Substrates	Used as high-quality carriers for the Pr:YLF chip, enabling robust packaging and integration into larger photonic circuits. 6CCVD offers substrates up to 10 mm thick.

Customization Potential

The realization of efficient, low-threshold waveguide lasers requires highly optimized resonator geometry, which 6CCVD is uniquely positioned to support:

Ultra-Smooth Facets: The paper highlights that better surface quality is expected via optimized dicing parameters. 6CCVD offers precision polishing services capable of achieving surface roughness (Ra) < 1 nm on SCD and < 5 nm on inch-size PCD, critical for minimizing scattering losses and maximizing coupling efficiency.
Custom Metalization for Resonators: The conclusion suggests depositing mirrors directly onto the waveguide end facets. 6CCVD provides in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for creating high-reflectivity mirror stacks or contact pads directly onto diamond substrates or integrated chips.
Custom Dimensions: 6CCVD can supply SCD or PCD wafers/plates in custom dimensions up to 125 mm, accommodating scaling requirements for future high-volume integrated photonics manufacturing.

Engineering Support

6CCVD’s in-house PhD engineering team specializes in the material science of MPCVD diamond and its application in high-performance optics and thermal management. We can assist researchers and engineers in:

Selecting the optimal diamond grade (SCD vs. PCD) for specific tooling or heat spreading requirements in integrated visible laser projects.
Designing custom metalization layers for resonator mirrors or electrical contacts.
Providing material consultation to minimize thermal effects and maximize the efficiency of similar ion-implanted waveguide devices.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Planar optical waveguides were fabricated in Pr:YLF crystals by ion implantation. In a further step, ridge waveguides were fabricated using precision diamond dicing. These enable strong light confinement and have propagation losses as low as 0.4 dB/cm. To study the influence of ion implantation on the spectroscopic properties, fluorescence and lifetime measurements were conducted in the ridge waveguides. Under blue pumping, small-signal optical gains of 6.5 dB/cm and 5 dB/cm were demonstrated at wavelengths of 607 nm and 639 nm, respectively. These results make ion-implanted ridge waveguides in Pr:YLF promising candidates for compact integrated lasers in the visible spectral region with high output powers in the watt range.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app15094956

References

2002 - Femtosecond laser-inscribed optical waveguides in dielectric crystals: A concise review and recent advances
2019 - Direct UV written integrated planar waveguides using a 213 nm laser [Crossref]
2010 - Carbon ion implanted Nd:MgO:LiNbO3 optical channel waveguides: An intermediate step between light and heavy ion implanted waveguides [Crossref]
2007 - Development of ion-implanted optical waveguides in optical materials: A review [Crossref]
2019 - Fabrication of low loss channel waveguide in tungsten-tellurite glass by 11 MeV carbon ion microbeam for telecom C band
2001 - Permanent narrow-band reflection holograms for infrared light recorded in LiNbO3:Ti:Cu channel waveguides [Crossref]
2021 - Watt-level 775 nm SHG with 70% conversion efficiency and 97% pump depletion in annealed/reverse proton exchanged diced PPLN ridge waveguides [Crossref]
2016 - Out of the blue: Semiconductor laser pumped visible rare-earth doped lasers [Crossref]
2022 - Visible solid-state lasers based on Pr3+ and Tb3+ [Crossref]