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Photonic Crystal Fiber (PCF) can provide characteristics that ordinary optical fiber do not exhibit, such as: single mode operation from the UV to IR with large mode-field diameters, highly nonlinear performance for super continuum generation, numerical aperture (NA) values ranging from very low to about 0.9, optimized dispersion properties, and air core guidance, among others. Applications for photonic crystal fibers include spectroscopy, metrology, biomedicine, imaging, telecommunication, industrial machining, and military, and the list keeps growing as the technology becomes a mainstream. Photonic crystal fibers are generally divided into two main categories: Index Guiding fibers that have a solid core, and Photonic Bandgap or air guiding fibers that have periodic micro-structured elements and a core of low index material (e.g. hollow core). A Classification tree is shown below in Fig. 1. Newport offers F-SM Series Large Mode Area, endlessly single-mode PCFs, F-NL Series Highly Nonlinear PCFs, and F-AIR Series Photonic Bandgap fibers, manufactured by Crystal Fibre, the biggest commercial supplier of photonic crystal fibers. Also offered is the SCG-800 and SCG-800-CARS self contained Supercontinuum Generators (see Supercontinuum Generation Fiber Devices). Please refer to our Fiber Tutorial Section (see Tutorial on Fiber Optics) for more detailed information on the properties of photonic crystal fiber. Newport's broad photonic crystal fiber selection provides the customers with the highest performance, most widely used fiber products. For adding fiber connectors and protective jackets, please contact Newport technical support.
The following volume discount schedule is automatically applied when ordering bare optical fiber: 6 - 20 m with 15 %, 21- 100 m with 22 %, > 100 m with 25 % |
Fig. 1 - Overview of the various classes of Photonic Crystal Fibers
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Index Guiding PCF |
Large Mode Area PCFs (F-SM Series) |
The F-SM Series PCFs are un-doped silica fibers that use a triangular pattern of air holes to form the cladding. Since the index contrast between the core and the cladding, Δn, is determined only by the geometry of the air holes, it is possible to fabricate fibers with a very small and accurate Δn, and thus obtain very low numerical apertures and very large mode areas. Furthermore, this type of fiber is single-mode over a very broad wavelength range, with a practically constant mode-field diameter (MFD). At short wavelengths, the fibers' performance is limited by macro-bending losses, which determines the practical wavelength range for applications. The F-SM series of fibers are optimized in order to obtain the largest possible MFD without introducing significant macro-bending losses on typical bending radii of more than 16 cm. See graphs in the Specifications Section below. |
End face image and weakly transmitted cladding modes profile of Newport's F-SM series micro-structured fiber using an MBP series imaging device (see Micro-Beam Profiler), with lighting on both the ends of a short price of the photonic crystal fiber.
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Applications |
The F-SM Series PCFs are typically used where single-mode, high-power delivery is required without introducing non-linear effects. Furthermore, they are the optimal choice for applications requiring single-mode guidance in a very broad wavelength range, e.g. in sensors, spectroscopy, interferometry or RGB displays. |
Free Space Coupling and Handling |
Coupling light into and out of an F-SM fiber is as simple as for standard doped-glass optical fibers. In a free-space set-up, the optics should match the NA of the fiber and be diffraction limited in order to obtain a low-loss coupling. Since the MFD is practically constant, the NA is proportional to the wavelength, which should be considered in the design of coupling optics for a broad wavelength range. The F-SM Series may also be spliced to standard fibers (available on a semi-custom basis), making them easy to integrate into existing systems or instruments. Optional beam expansion FC connectors enhance high power capabilities. |
Nonlinear PCFs (F-NL Series) |
Nonlinear PCFs are of the high-index-guiding type (see Fig. 1), and they are designed with a small core to get a high nonlinear coefficient. The air-filled microstructured cladding region of nonlinear photonic crystal fibers lends this fiber type several advantages compared to standard technology step-index fibers. The high index difference between the silica core and the air-filled microstructure enables tight mode confinement resulting in a low effective area and thereby a high nonlinear coefficient. The air-filled region also results in strong wavelength dependence in the characteristics of the fiber and is responsible for the large wave-guide dispersion possible in such fibers. The wave-guide dispersion can be used to enhance or cancel out the material dispersion in the fiber and the flexibility in terms of dispersion profile is therefore much bigger in PCFs than in standard fibers. Changing the design of the microstructure (hole-sizes, pitch, hole structure) strongly influence the wave-guide dispersion and it is possible to design fibers with zero dispersion wavelength (ZDW) in the visible wavelength range or with flat near-zero dispersion over a large wavelength range. By choosing the dispersion profile carefully, the fibers can be tailored to facilitate different nonlinear processes.
Newport's F-NL Series nonlinear fibers are designed with relatively small holes to be single-mode at the operation wavelength. This approach has several advantages compared to multimode nonlinear fibers with large air holes. First, the fibers are easier to splice to solid standard fiber due to the lower air-filling fraction. Second, alignment and focusing with free-space coupling is less critical as light focused on the cladding region will not be coupled, unlike in high-air-filling fraction fibers, where light can be guided in the silica "islands" between the large holes. Finally, a long range of applications requires strict single-mode operation |
Supercontinuum in PCFs |
For Supercontinuum Generation made easy, try Newport's new SCG-800 self contained Supercontinuum Generator. The SCG-800 consists of a nonlinear Photonic Crystal Fiber contained in a robust, sealed, 25mm metal housing. Simply pump the SCG-800 with an 800nm femtosecond laser and enjoy octave-spanning output without the hassle of fiber handling and cleaving. Download the SCG-800 datasheet for more information. |
Supercontinuum generated using F-NL series PCF illuminated with a femtosecond laser
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Photonic Bandgap, or Air-Guiding Fibers (F-Air Series) |
One very exciting feature of the PCF technology is the possibility of realizing fibers that guide light in a hollow (air) core. Contrary to the case of conventional index-guiding fibers (and our broad range of index-guiding PCFs) these fibers guide light using the Photonic Bandgap (PBG) effect. The highly periodic structure of air holes in the cladding of the fiber creates a photonic bandgap. This means that light of frequencies within the PBG is not allowed to propagate out through the cladding and may be trapped in the core of the fiber. In contrast to index-guiding fibers, there is no requirement on the refractive index of the core region to be larger than the index of the cladding. An inherent feature of PBG-Guiding is that the fiber only guides light in a limited spectral region. For fibers guiding around 1550nm, a typical bandwidth is ~200nm. Outside this region, the fiber core is anti-guiding. A typical transmission spectrum is shown in Fig. 2 below. |
Fig. 2 - Typical transmission spectrum for an airguiding fiber
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Extreme dispersion properties may be found in the PBG fibers, such as anomalous dispersion values in the thousands of ps/nm/km. Due to a negligible contribution from the core material (air), the total dispersion of PBG fibers is dominated by wave-guide dispersion. |
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Newport is dedicated to bringing you the latest in the new and exciting field of Photonic Crystal Fibers. For the most recent additions to our product line and up-to-date specifications, please see the Photonics section of Newport's website (www.newport.com). |
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NA & MFD vs. Wavelength for F-SM8 fiber
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Attenuation vs. Wavelength for F-SM20 fiber
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NA & MFD vs. Wavelength for F-SM20 fiber
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NA & MFD vs. Wavelength for F-SM25 fiber
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Attenuation vs. Wavelength for F-NL-PM-750 fiber
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Dispersion vs. Wavelength for F-NL-PM-750 fiber
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Related Products |
For a cost effective digital imaging device for viewing fiber endface and observing mode profiles, see Micro-Beam Profiler
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