Coherent PLMA-TDF-25P/400-HE Coherent Optical Fiber

Condition: New
Part #: PLMA-TDF-25P/400-HE

$1,132.50

SKU: PLMA-TDF-25P/400-HE Category:
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Description

The Coherent PLMA-TDF-25P/400-HE is a premier Polarization-Maintaining (PM) Large Mode Area (LMA) Thulium-doped double-clad fiber, engineered for high-performance applications in the 2μm wavelength range. Operating within the 1900–2100 nm “eye-safe” mid-infrared band, this high-efficiency (HE) fiber is optimized for 793 nm laser pumping.

Designed for demanding industrial and medical environments, the PLMA-TDF-25P/400-HE balances ultra-high photoelectric conversion efficiency with superior beam quality. Its robust construction ensures long-term reliability for system integrators seeking to develop high-power continuous-wave (CW) or pulsed fiber lasers with minimal nonlinear distortions.


Core Technology and Design

The PLMA-TDF-25P/400-HE utilizes a sophisticated Pedestal Core Structure. This design is critical for managing the high power density found in Large Mode Area fibers. By incorporating a low Numerical Aperture (NA) core, the fiber facilitates excellent single-mode beam quality even at high power levels.

The double-clad geometry features a high-index core, a 400 μm inner cladding for pump light guidance, and a low-index acrylate outer coating. This configuration allows for high pump absorption rates, reducing the required fiber length and subsequently lowering the threshold for nonlinear optical effects like Stimulated Brillouin Scattering (SBS) and Stimulated Raman Scattering (SRS).


Mechanism of Action

The fiber operates on the principle of Thulium (Tm³⁺) ion sensitization. When pumped at 793 nm, the Thulium ions undergo a cross-relaxation process that allows for a “two-for-one” photon conversion, where one pump photon can result in two signal photons in the 2000 nm range.

  1. Pump Absorption: The 793 nm pump light is injected into the inner cladding and absorbed by the Tm-doped core.

  2. Energy Conversion: The high Thulium concentration and “HE” optimization enable efficient transition to the $^3F_4 \rightarrow ^3H_6$ energy levels.

  3. Polarization Maintenance: Built-in stress elements create high birefringence (Nominal $2.5 \times 10^{-4}$), ensuring that the output laser maintains a stable, linear polarization state, which is vital for frequency doubling or external modulation.


Key Advantages

  • High Conversion Efficiency: The “HE” designation signifies optimization for maximum slope efficiency, significantly reducing thermal load.

  • Short Gain Length: High pump absorption ($4.80 \text{ dB/m}$ at 793 nm) allows for shorter fiber lengths, which minimizes nonlinearities and maintains pulse integrity.

  • Superior Beam Quality: The $25 \text{ μm}$ core with a $0.090 \text{ NA}$ supports a large mode area while maintaining a near-diffraction-limited beam.

  • High Mechanical Reliability: Tested at $\ge 100 \text{ kpsi}$, the fiber is designed to withstand the stresses of tight coiling in compact laser modules.

  • Advanced Coating: The low-index acrylate coating provides a high inner cladding NA ($\ge 0.46$), ensuring efficient pump light confinement.


Applications and Uses

  • Medical Lasers: Ideal for surgical scalpels and dermatological treatments due to the high water absorption in the 2μm band, providing precise tissue ablation and coagulation.

  • Industrial Processing: Used in plastic welding and transparent material processing where mid-infrared wavelengths are more effective than standard 1μm lasers.

  • LiDAR and Sensing: The “eye-safe” nature of the 1900–2100 nm band makes it perfect for long-range Laser Radar (LiDAR) and atmospheric monitoring.

  • Defense & Aerospace: Used in directed energy systems and IR countermeasures where polarization stability is a mission-critical requirement.

  • Solid-State Pumping: Serves as a high-brightness pump source for Ho-doped solid-state lasers or OPOs.


Technical Specifications

Parameter Specification
Dopant Thulium ($Tm^{3+}$)
Operating Wavelength 1900 – 2100 nm
Core Diameter $25.0 \pm 2.5 \text{ μm}$
Cladding Diameter $400.0 \pm 15.0 \text{ μm}$
Coating Diameter $550.0 \pm 20.0 \text{ μm}$
Core NA $0.090 \pm 0.010$
Inner Cladding NA $\ge 0.46$
Pump Absorption (793 nm) $4.80 \text{ dB/m}$
Birefringence (Nominal) $2.5 \times 10^{-4}$
Proof Test Level $\ge 100 \text{ kpsi}$

Frequently Asked Questions

What are the primary benefits of the “HE” high-efficiency optimization?

The HE optimization in the PLMA-TDF-25P/400-HE maximizes the photoelectric conversion efficiency through enhanced Thulium cross-relaxation. This allows for higher output power with lower waste heat generation, leading to improved thermal management, better beam stability, and a smaller overall footprint for the laser system.

Why is polarization maintenance important for 2μm fiber lasers?

Polarization maintenance is crucial for applications involving frequency conversion, coherent beam combining, or external modulation. By ensuring the light remains in a fixed linear state (birefringence of $2.5 \times 10^{-4}$), this fiber eliminates power fluctuations caused by polarization drift and enables more precise control in scientific and industrial systems.

Can this fiber be used for both CW and pulsed laser applications?

Yes. The Large Mode Area (LMA) design and $25 \text{ μm}$ core diameter effectively reduce the power density within the fiber. This allows the PLMA-TDF-25P/400-HE to handle high-peak-power pulses with minimal nonlinear effects while also supporting high-average-power Continuous Wave (CW) operation for industrial and medical use.

Why is the 1900–2100 nm wavelength referred to as “eye-safe”?

Light in the 2μm band is absorbed by the cornea and lens of the human eye before it can reach the sensitive retina. While high-power lasers always require safety precautions, this “eye-safe” characteristic significantly reduces the risk of permanent retinal damage compared to 1μm or visible lasers.

What is the role of the low-index acrylate coating?

The low-index acrylate coating acts as the second cladding layer, creating a high Numerical Aperture ($\ge 0.46$) for the inner cladding. This maximizes the acceptance angle for pump light, allowing for more efficient coupling from high-power 793 nm diode lasers and reducing pump leakage.

How does the pedestal core structure improve beam quality?

The pedestal structure allows for a precisely controlled, low core Numerical Aperture ($0.090$). This design suppresses higher-order modes in the large $25 \text{ μm}$ core, ensuring that the fiber delivers a high-quality, single-mode-like beam necessary for precision medical surgery and long-range LiDAR applications.

Listing Terms & Conditions

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