Single-mode fibers (also single mode optical fiber, SMF, SM fiber, and monomode fiber) are designed to allow only one propagation mode (transverse mode) per polarization direction, retaining the fidelity of each light pulse over longer distances and providing higher bandwidth, when compared to multi-mode optical fibers.
Typically, a standard single-mode optical fiber has a relatively small core diameter between 8 and 10.5 µm, a cladding diameter of 125 µm, and a small difference in refractive index between the cladding and the core. Single-mode fibers are commonly comprised of a silica core and silica cladding, utilizing a step-index refractive index profile. The core, for example, would be doped to create the difference in index of refraction between the cladding and the core.
While the small core diameter does not allow for a great deal of power, it does allow only the primary transverse mode to be guided along the fiber. This primary mode subsequently travels down the fiber in an essentially straight line, and therefore, does not suffer from pulse spreading, which is common in multimode fiber because of varying path lengths. This allows for an increased bandwidth in a single-mode fiber, as the laser light travels the same distance at the same speed.
Another benefit, adding to the larger bandwidth, is the lack of intermodal dispersion in single-mode optical fibers. This fiber type is therefore able to transmit signals at longer distances while retaining the fidelity of each pulse of light when compared to multimode fibers. Single-mode fiber does suffer from some distortion of the signal. However, this distortion is mainly caused by chromatic dispersion and is very small compared to the modal dispersion inherent to multimode optical fiber. Furthermore, the utilization of the primary mode, along with higher wavelengths (≈ 1.3µm and ≈ 1.5µm) results in a low level of attenuation. The increased bandwidth, retained pulse fidelity, and low attenuation provides great benefits in optical fiber communication, for example, with high data rates transmitted over long distances.
Our Single-Mode Fiber Laser Products
RPMC Lasers is your Single-Mode Fiber Laser supplier! We offer a wide range of SM fiber output lasers, including Laser Diode Modules, CW DPSS Lasers, CW Fiber Lasers, Multi-Wavelength Beam Combiners, Single-Emitter Laser Diodes, Distributed Feedback (DFB) Lasers, Volume Bragg Grating (VBG) Laser Diodes, Superluminescent Laser Diodes (SLEDs or SLDs), and Turn-Key configurations. Among these options, we provide many wavelengths in the UV, violet, blue, green, yellow, red NIR, and SWIR spectral regions (and multiple wavelength output), many power options up to 500 mW (0.5 W), and narrow linewidth output options.
Deeper Dive into Single-Mode Fiber Output Lasers
Multimode vs Single-Mode Lasers for Raman Spectroscopy
The first question you should ask yourself when considering which type of laser to choose is whether you are doing microscopy or bulk sampling. If the answer to that question is microscopy, then you immediately should go with a single mode laser. Since the goal of any microscopy system is to produce the highest resolution image possible, the number one consideration should be how tightly can the laser beam be focused down. In optics, the M2 of a laser determines how small of a spot size can be achieved for a given microscope objective with an M2 of 1 being the best possible focus. Even though a perfect M2 of 1 can never be physically achieved, open beam single mode diode lasers can typically have a M2 < 1.5 and single mode fiber-coupled diode lasers have an M2 »1.05.
HeNe Lasers vs Diode Lasers: HeNe Laser Pros and Cons
Despite of so many good intrinsic properties, HeNe lasers often do not meet the requirements of today’s industrial environments. Industrial production lines with 24/7 operation are all about robustness and long lifetime, thus industrial instrument manufacturers tend to pay 2 to 4 times more for a laser, which has a longer life-time, is easier to replace and maintain.
The price difference from HeNe lasers mainly depend on how many parameters of semiconductor lasers have to be close to the performance of HeNe. If one needs perfect beam quality, single-mode or polarization maintaining fiber has to be used to achieve <1.05 M2, nice round beam shape and diffraction limited divergence. Reasonably good central wavelength stability can by achieved by good temperature and power stabilization of the semiconductor emitter. Most difficult and expensive to achieve is the long coherence length requirement. Most popular way of ensuring high coherence length and very stable (<5 pm) central wavelength is to apply external cavity designs (ECDL – external cavity diode laser) by using volume Bragg gratings or fiber Bragg gratings.
While there are countless varieties of fiber optics available on the market today, the two most important factors when discussing how the output of diode laser can be coupled into a fiber are its core size and numerical aperture. Therefore, in this blog post, we are going to first take a brief look at the physical significance of these two parameters, and why they are so crucial to laser diode coupling. In part 2 of this blog post, we will then go on to examine common fiber coupling techniques used in commercial fiber coupled laser diode packaging.
In the last blog post of our laser diode fundamentals series, we discussed the basics of fiber optics concentrating on two key parameters; core diameter and numerical aperture. We mentioned how the numerical aperture depends on the relationship between the index of the core and the cladding, and that this directly relates to the angular acceptance cone of the fiber optic. We also discussed how the core diameter in conjunction with the laser wavelength determines the spatial mode structure of the light guided through the fiber. This is why single mode fiber coupled laser diodes are far more prevalent in the infrared range then they are in the ultraviolet for example, the shorter wavelengths require smaller core diameters…
Why Should Single-Mode Fibers Have an Angle Polished?
While back reflections are definitely problematic for lasers in general, they are most problematic for single-mode lasers. Especially single-mode diode lasers. There are two primary reasons for this extreme sensitivity. As we discussed in our previous blog post titled “Laser Diode Fundamentals: Single Longitudinal Mode Diodes,” injection seeding can change the gain threshold of a laser. In that blog, we explained that by controlling the feedback into the laser you could select specific longitudinal modes. Similarly, when unwanted back reflections exist in the system, it will change the gain threshold in unintended ways and cause the longitudinal mode structure to destabilize.
Pros & Cons of Pigtailed Laser Diodes vs. Detachable Fiber-Coupled
For single-mode fibers the core diameter needs to be tiny, typically less than 10 microns, to ensure that no higher-order modes can propagate through the fiber. On the other hand, multi-mode fibers can have a wide range of core diameters ranging from 62.5 microns upward on 1 mm. Both of these fiber types are widely used with laser diodes depending on the needs of the application. For example, when the beam profile is essential, such as in microscopy, single-mode fiber is almost always preferred. By contrast in an application, such as laser cladding, where power is most important a multi-mode fiber would be the obvious choice.
Choosing the Right Connector for Your Fiber-Coupled Laser Diode
There are two main categories of fiber-coupled laser diodes, pigtailed and detachable. The pigtailed approach provides significant advantages when it comes to alignment stability, mainly when dealing with single-mode fibers which, typically have a core diameter of less than 10 microns. By comparison, it is impossible to ensure that detachable fiber-optics will line up in the same spot, each time the fiber is connected. Therefore, reducing the overall coupling efficiency of the system. However, unless the pigtail is fusion spliced to another fiber, for both pigtailed and detachable fibers, it is required that at least one end of the cable be terminated with a fiber-optic connector. As a result, it is essential to understand the different types of fiber connectors used with fiber-coupled diode lasers as well as their pros and cons.
With over 25 years experience providing single-mode fiber output lasers to OEM integrators working in different markets and applications, and 1000s of units fielded, we have the experience to ensure you get the right product for the application. Working with RPMC ensures you are getting trusted advice from our knowledgeable and technical staff on a wide range of laser products. RPMC and our manufacturers are willing and able to provide custom solutions for your unique application.
If you have any questions, or if you would like some assistance please Contact Us here. Furthermore, you can email us at [email protected]to talk to a knowledgeable Product Manager.
Alternatively, use the filters on this page to assist in narrowing down the selection of single-mode fiber lasers for sale. Finally, head to our Knowledge Center with our Lasers 101 page and Blogs, Whitepapers, and FAQ pages for further, in-depth reading.
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The FL CW/CW Modulated Series offers a variety of standard and custom CW fiber laser options. Available in both OEM and Turnkey formats, our 1um, 1.5um and 2um fiber lasers are manufactured to Telcordia standards and can be modified to meet your applications requirements. With available powers up to 100W at 1um, 30W at 1.5um and 40W at 2um, our CW fiber lasers are suitable for a wide range of applications. Available options and configurations include narrow linewidth, single frequency outputs, C and L-band broadband sources, PM fiber options, power tunability and high-speed trig./mod. Customized configurations are available upon request.
The Matchbox series offers excellent performance and reliability in the “World’s Smallest” ultra-compact, all-in-one, integrated laser head. They can operate on a 5V power supply while maintaining low noise operation. The monolithic design of the Matchbox Series laser includes thermally stabilized optics in a hermetically sealed housing, ensuring reliable and maintenance-free operation. This series is available in wavelengths from 405 nm thru 1064nm, with options for collimated beam or fiber-coupled output, and single-mode and multimode versions.
The LaserBoxx Low Noise series of CW diode laser modules, with a variety of wavelengths from 375 to 785nm and output powers up to 350mW,offers highly customizable laser solutions for OEM and plug & play modules. With advanced features such as excellent beam quality, stability, and modulation capabilities, our lasers provide ultra-low noise and a wide range of options for SM, MM, and PM fiber coupling. Our dedicated control software, USB and RS232 interfaces, and external controller with power display make integration, operation, and remote diagnostics a breeze. Additionally, our rugged and compact design and wide variety of standard wavelengths ensure that our lasers can meet your specific needs.
The LaserBoxx-SLM series are single longitudinal mode (SLM) CW diode laser modules available in green, yellow, red, and NIR wavelengths, delivering ultra-narrow linewidths, with excellent temperature stability and low noise current. Embedded firmware locks the laser on the same mode at each startup. This customizable, compact, self-contained laser module is available in turn-key or OEM versions and utilizes a proprietary alignment-free, monolithic resonator, and comes standard with a graphic user interface with remote diagnostics via USB, RS232, or direct I/O interface. With modulation capabilities and adjustable power options, the SLM Series is versatile and adaptable to a wide range of applications.
The LXCc series is a range of compact, highly customizable, and flexible all-in-one laser combiners that provide the widest variety of wavelength options, up to 7 different laser lines (up to 500 mW output power per line), direct modulation on every source, SLM capabilities, proven long-term stability, and many other advanced features. The turnkey or OEM versions allow a large choice of lasers from 375nm up to 1064nm. The extension module provides the ultimate level of flexibility with options for up to 4 optical fiber outputs, AOTF modulator, motorized ND filter, integrated fast switching output ports for FRAP, or adjustable split power for light-sheet microscopy.
The REP series includes high-performance, tunable, single-frequency (DFB-like) diode lasers and Fabry-Perot laser diodes in wavelengths from 1270nm thru 2350nm, designed to address challenges in Gas Sensing, LIDAR, Spectroscopy, and Telecom. The REP series includes high-power and narrow linewidth options, covering various product ranges at the most popular wavelengths, providing customizable units with multiple packaging options, including the Fiber coupled 14-pin butterfly, TO39 (w/TEC), and TO56. For a complete module incorporating the fiber-coupled butterfly package with an integrated current driver and TEC controller, designed for ease of operation, it is the ideal platform for high stability gas detection or remote sensing. See the DX1 Series.
The RML series of laser diode modules are available with single mode fiber outputs with a set wavelength from 405nm – 2500nm. The compact RML series is available with up to 80mW of output power in a package measuring 15mm in diameter and 40mm in length (without connector) . As an option these modules are offered with a potentiometer for power adjustment, external TTL modulation up to 1MHz and analog modulation up to 100kHz.
The RPK Series of multiple, single-emitter fiber-coupled diode lasers are available in wavelengths from 405nm thru 1550nm with up to 300W output power. Our specialized fiber-coupling techniques ensure high efficiency, stability, and superior beam quality, while rigorous inspections and burn-in procedures guarantee each product’s reliability, stability, and long lifetime. Highly customizable packages allow us to meet our customers’ specific needs, providing high-quality products at reasonable prices.
The RWLP series offers an affordable and versatile solution for your laser application needs with single-mode and multimode options and wavelengths from 405nm thru the IR region. With customizable options, our team can work with you to solve any challenges you may face. Rigorously tested for long-term reliability, the RWLP series ensures consistent performance and high beam quality. Perfect for integration, this series supports multiple applications including biological and analytical instrumentation.
The RWLS series of RGB White Laser Diodes offers customizable, versatile, and reliable solution for your laser applications. Available in a wide range of power levels, with three base wavelengths: 635 nm (Red), 520nm (Green), and 445nm (Blue), the RWLS series can be tailored to your exact specifications. Typically packaged in a pigtailed HHL configuration, with built-in TEC, there are also plenty of customization options including wavelength, power, and packaging.