Gooseneck Y-BundleThe OSL2YFB Gooseneck Y-Bundle (Bifurcated) Cable splits the output of the fiber light source into two independently positionable beams, allowing larger work areas to be illuminated. Unlike the fiber bundle included with the OSL2 and OSL2IR, each leg of this bifurcated cable has a gooseneck jacket for easy manual positioning.

Because the WFA1000 and WFA1100 trans-illumination modules need a Ø1" collimated light source secured to a 30 mm cage system to provide even illumination, the emitted beam from the OSL2 must be collimated by a plano-convex lens with a focal length of 60.0 mm. We recommend using either the LA1134 or LA1134-A N-BK7 plano-convex lens. The LA1134 lens is uncoated and will provide relatively even transmission of the entire OSL2 spectrum; the LA1134-A features an AR coating that provides improved transmission in the 350 - 700 nm range but worse transmission above 700 nm. See the Coatings Tutorial for details. A slightly longer focal length lens can be substituted, but will result in dimmer illumination at the sample plane.

These light sources have a built-in protection mechanism to prevent the unit from overheating and to turn off the lamp when the access door is opened. The LED indicator on the front panel is green during normal operation. If the unit overheats, power to the lamp is cut off and the LED turns red. If the access door is opened during normal operation, power to the lamp and the LED are cut off.

These collimation and focusing packages are designed for use with the fiber bundle included with the OSL2 and OSL2IR light sources; the fiber bundle included with the former OSL1 light source; and the replacement fiber bundles sold above. Two 6-32 setscrews that accept a 1/16" hex key secure the tip of the fiber bundle into the back of the collimation or focusing package. Internal SM05 (0.535"-40) threads on the front of each package and a 0.70" (17.8 mm) outer diameter make these directly compatible with our family of Ø1/2" lens tubes and components.

The OSL2 and OSL2IR have built-in universal power supplies and include a location-specific detachable power cord. Additional user-replaceable light bulbs can be purchased below. To order the OSL2 or OSL2IR without the included fiber bundle, or for general custom order inquiries, please contact Tech Support.

Steady state fluorescence spectra are when molecules, excited by a constant source of light, emit fluorescence, and the emitted photons, or intensity, are detected as a function of wavelength. A fluorescence emission spectrum is when the excitation wavelength is fixed and the emission wavelength is scanned to get a plot of intensity vs. emission wavelength.

Our fiber ring illuminator provides lighting very nearly aligned to the optical axis of the microscope that is shadow-free and uniform across the sample plane and throughout the entire working distance (WD) range. The use of 5 fiber rings increases the light intensity and WD range compared to illumination from a single fiber ring.

Thorlabs offers three different replacement bulbs for the OSL2 and OSL2IR High-Intensity Fiber Light Sources. The OSL2B is identical to the original bulb that comes with the OSL2, and the OSL2B2 is a high-power variant of the OSL2B. The OSL2BIR is identical to the original bulb that comes with the OSL2IR. The OSL2B and OSL2B2 bulbs each have an integrated hot mirror that blocks most of the IR light. In contrast, the OSL2BIR provides enhanced output in the near-IR due to the aluminum-coated reflector and lack of integrated hot mirror. The graph below compares the spectra and power of these bulbs. To view a spectrum and raw data for each individual bulb, click on the graph icons in the table below.

Thorlabs' Fiber Connector Adapters allow fiber patch cables and bundles with standard connectors to be used with the OSL2 and OSL2IR light sources (see photo to the right). Vacuum-compatible versions of the SM1FC and SM1SMA are available; the SM1SMAV and SM1FCV adapters are both vacuum compatible down to 10-10 Torr. Please note that the light output from fiber patch cables or bundles will be lower than that of the fiber bundle included with the OSL2 and OSL2IR, due to the smaller core or effective core diameter and lower NA. We recommend verifying that any other fiber bundle used with the OSL2 or OSL2IR light sources can sustain the heat from the bulb; please contact Tech Support with inquires.

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Thorlabs’ FRI61F50 Fiber Ring Illuminator has a 915 mm (36.02") long fiber bundle that couples light from our OSL2 and OSL2IR Fiber Light Sources into a Ø55 mm ring illuminator composed of five concentric fiber rings. The illuminator easily mounts onto most standard upright microscopes, such as the one shown to the right. It is secured using three thumbscrews, each of which is nylon tipped to produce adequate holding friction while preventing scratching or marring of the microscope. The fiber ring slips around any objective housing with a diameter of 60 mm or less.

To connect a patch cable, the fiber bundle adapter that comes preinstalled on the OSL2 or OSL2IR must first be removed by unscrewing it from the output port. Next, thread the fiber connector adapter into the output port. Each disk has four dimples, two in the front surface and two in the back surface, that allow it to be tightened from either side using either the SPW909 or SPW801 spanner wrench. The dimples do not go all the way through the disk so that the adapters can be used in light-tight applications. For Thorlabs' full line of SM1-threaded adapters, see Terminated Fiber Adapters.

Fluorescence, specifically, is a type of photoluminescence where light raises an electron to an excited state. The excited state undergoes rapid thermal energy loss to the environment through vibrations, and then a photon is emitted from the lowest-lying singlet excited state. This process of photon emission competes for other non-radiative processes including energy transfer and heat loss.

The OSL1-SMA adapter inserts into the front panel of the former OSL1 unit and is secured by a thumbscrew. It is compatible with SMA905- and SMA906-style connectors.

When the term “fluorescence” is used, the same methods of measurement can typically be applied to any of the above categories of luminescence.

Thorlabs' OSL2 and OSL2IR High-Intensity Fiber Light Sources deliver white light for brightfield microscopy, laboratory, and illumination applications. The output illumination intensity is exponentially variable from 0 to 100% using a knob on the front of the unit. The 150 W EKE halogen bulbs have a 3200 K color temperature (see the graph to the right) and are user replaceable with optional bulbs sold below. These portable fiber-coupled light sources are compatible with 100 to 120 VAC as well as 220 to 240 VAC and includes a location-specific power cord.

The fiber illuminator's output port also has internal, 3.5 mm deep SM1 threads. The unit is shipped with a fiber bundle adapter installed in these threads. By removing the fiber bundle mounting adapter from the output port, standard fiber connector adapters (sold below) and other SM1-threaded components can be attached to the light source.

Fluorescence spectroscopy uses a beam of light that excites the electrons in molecules of certain compounds, and causes them to emit light. That light is directed towards a filter and onto a detector for measurement and identification of the molecule or changes in the molecule.

A 91 cm (36") long fiber bundle with a Ø6.4 mm (Ø0.25") effective core is included with the OSL2 and OSL2IR light sources. To adapt the fiber bundle output to an optomechanical setup, we recommend using our AD8F mounting adapter (see photo to the left), which provides external SM1 (1.035"-40) threading for easy integration with any of our SM1-threaded components. In particular, this adapter can be used to connect the OSL2 or OSL2IR to a Cerna® microscope for both epi-illumination and trans-illumination; see the Use with Cerna tab for details.

To install the replacement bulb in the former OSL1 source, simply loosen the two fasteners on the front panel of the unit, slide out the bulb assembly, and remove the old bulb. Details are available in Chapter 4 of the OSL1 manual, available as a PDF here. The OSL1B bulb can also be installed in our OSL2 or OSL2IR light source by following the installation instructions in Chapter 5 of the OSL2 manual or OSL2IR manual.

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The photo to the right illustrates one way to filter the output light from the OSL2 lamp using a mounted Ø25.0 mm filter. For details on alternate configurations using unmounted Ø12.5 mm or Ø25.0 mm filters, please click the photo.

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The OSL2 comes with a pre-installed OSL2B bulb that has an integrated hot mirror that blocks the majority of the IR light and has a typical wavelength range of 400 - 1600 nm. The OSL2IR comes with the OSL2BIR bulb which provides enhanced output in the near-IR due to the aluminum-coated reflector and lack of integrated hot mirror; it has a typical wavelength range of 400 - 1750 nm. Please see the Specs tab for more details.

Fluorescence spectroscopy is an investigative method based on the fluorescence properties of the sample under study, and is used for quantitative measurements of chemical products.

The cage plates should be separated such that the distance between the fiber tip and the plano side of the lens is 2.23" (56.7 mm), the back focal length of the lens. The cage system provides easy adjustment of the distance between the cage plates while maintaining alignment. Please contact Technical Support if you need further assistance with this installation.

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To assemble the cage system for the OSL2, first mount the lens onto a SM1 (1.035"-40) threaded 30 mm cage plate (Item # CP33(/M)) using the included retaining rings (Item # SM1RR). The other cage plate secures the Ø8 mm to SM1 adapter (Item # AD8F); utilize an additional retaining ring to set the adapter at a particular position. Attach the cage rods (Item # ER3-P4) to the trans-illumination module by removing the dust cover on the side of the module with a 1.5 mm hex, then locking the cage rods into place using the exposed side-locking 4-40 setscrews (0.05" hex). Once the cage rods are secure, slide the cage plate with the optic onto the rods so that the convex side of the lens faces the trans-illumination module. This is then followed by the cage plate with the AD8F adapter. The cage plates are secured to the cage rods using side-locking 4-40 setscrews. Once the assembly is secure, mount the tip of the fiber bundle onto the end of the collimation package using two 6-32 setscrews [1/16" (1.5 mm) hex]. See the diagram and images below for a visual depiction of this assembly.

For the most comprehensive book on Fluorescence Spectroscopy please read Dr. Joseph Lakowicz’s book, Principles of Fluorescence Spectroscopy, third edition.

The OSL1-SMA fiber bundle adapter allows multimode fiber bundles with SMA connectors to be used as the output of our former OSL1 fiber light source. Our fiber bundles with SMA connectors offer broader operating wavelength ranges than the fiber bundle included with the former OSL1 and the OSL2YFB bifurcated fiber bundle (sold above), and they are available in longer lengths.

AccessoriesWe offer collimation and focusing packages for the end of the fiber bundle, single-output fiber bundles, a bifurcated fiber Y-bundle with two goosenecked legs, and a microscope ring illuminator. The single-output fiber bundles are available in two varieties: a metal-jacketed replacement bundle for the included bundle and a gooseneck bundle for increased rigidity and easy manual positioning. Longer length fiber bundles are also available as a custom order by contacting Tech Support.

Click to Download Raw DataThe typical long-term and short-term output intensity stability of the OSL2 and OSL2IR are shown above.

The OSL1B replacement light bulb is identical to that included with our former OSL1 light source. The bulb has an integrated hot mirror that blocks most of the IR light. Click on the graph icon in the table to the right to view the bulb's emission spectrum.

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The fiber ring illuminator can be attached to the OSL2 or OSL2IR using the included adapter. The two nylon-tipped setscrews can be tightened using the included 1/16" hex key. Our AD16F adapter is available as a replacement.

Fluorescence is a type of luminescence caused by photons exciting a molecule, raising it to an electronic excited state.

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The photos to the left show the light output from the fiber bundle included with the OSL2 lamp. The photo to the far left shows the highly divergent beam emitted from the fiber bundle when it does not have a lens assembly attached. The other two photos show the beam when the collimation and focusing packages are attached.

The term fluorescence refers to one type of luminescence. Luminescence, broadly defined, is light emission from a molecule. There are several types of luminescence.

These two spectral types (emission and excitation) are used to see how a sample is changing. The spectral intensity and or peak wavelength may change with variants such as temperature, concentration, or interactions with other molecules around it. This includes quencher molecules and molecules or materials that involve energy transfer. Some fluorophores are also sensitive to solvent environment properties such as pH, polarity, and certain ion concentrations.

If a higher color temperature is desired, our color-balancing filters can be used to attenuate red light from the OSL2 light source while passing blue light. This results in a beam with a higher color temperature and lower total power.

Thorlabs offers fiber bundles designed to be used with the OSL2 and OSL2IR Fiber Light Sources sold above. These cables have fiber tips with Ø7.9 mm (Ø0.31") outer dimensions, enabling them to be used in place of the fiber bundle included with the OSL2 and OSL2IR.

To install the replacement bulb in the OSL2 or OSL2IR sources, open the door on the top of the unit, as shown in the photo to the right, and remove the old bulb. Details are available in Chapter 5 of the OSL2 manual or OSL2IR manual.

Other molecules and materials such as fluorescent proteins, semiconductors, phosphors, and rare earth elements are among the commonly used fluorescent samples. Polymers with conjugated aromatics or dienes also commonly have fluorescent properties. Of course, new materials are being created all the time.

Clicking the icon in the table below will open a window that contains additional specifications, performance data, and drawings.

The OSL2 is compatible with a Cerna microscope via the single-cube epi-illuminator module (Item # WFA2001), which contains anti-reflective (AR)-coated optics with <0.5% average reflectance per surface over the 350 - 700 nm wavelength range. The halogen lamp fiber bundle and epi-illuminator module are connected together by an SM1-threaded (1.035"-40) adapter (Item # AD8F). First thread the adapter onto the epi-illuminator module, then secure the fiber bundle with the nylon-tipped setscrews on the adapter [1/16" (1.5 mm) hex]. The epi-illuminator module accepts an uncollimated light source, so no collimation package is necessary.

Thorlabs' High-Intensity Fiber-Coupled Light Sources are designed for illumination of brightfield microscopy setups and general-purpose laboratory use. A removable, 91 cm (36") long, Ø6.4 mm (Ø0.25") effective core fiber bundle is included with each light source. Replacement bundles are available below. Additionally, each light source has an internally SM1-threaded (1.035"-40) output port for custom integration into optomechanical setups.

Fluorescent molecules and materials come in all shapes and sizes. Some are intrinsically fluorescent, such as chlorophyll and the amino acid residue tryptophan (Trp), phenylalanine (Phe) and tyrosine (Tyr). Others are molecules synthesized specifically as stable organic dyes or tags to be added to otherwise non-fluorescent systems. There are entire catalogs of these available. Typically, organic fluorescent molecules have aromatic rings and pi-conjugated electrons in them. Depending on their size and structure, organic dyes can emit from the UV out into the near-IR.

The OSL2 high-intensity light source provides effective broad-spectrum illumination for brightfield and reflected light microscopy. It can be used in both epi-illumination and trans-illumination configurations within the Cerna microscopy platform.

Four replacement bulbs for use with our high-intensity fiber light sources are available below, along with their emission spectra. The OSL2B and OSL1B bulbs are identical to the bulbs used in the OSL2 and the former OSL1 light sources, respectively, and emit in the visible spectrum. The OSL2B2 bulb also emits in the visible spectrum and provides greater power output at the expense of bulb lifetime. Lastly, the OSL2BIR bulb is used in the OSL2IR light source and offers enhanced emission in the near infrared through the use of an aluminum-coated reflector. Further details on compatible bulbs are also provided on the Specs tab.

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Below is a selection guide for all of our white-light, broadband, lamp-based light sources. In addition to these sources, Thorlabs also offers unmounted white-light LEDs, white-light mounted LEDs, white-light fiber-coupled LEDs, and high-powered, white-light Solis® LEDs.

The FRI61F50 has a WD range of 50 - 170 mm. Using the illuminator at distances greater than 170 mm will result in low-intensity, even illumination, which may be acceptable depending on the application.

Gooseneck Single-Output Fiber BundleThe OSL2RFB Gooseneck Single-Output Fiber Bundle has the same fiber configuration as the bundle included with the OSL2 and OSL2IR, but has a gooseneck jacket for stability and easy manual positioning. The gooseneck jacket allows the bundle to maintain its position once it has been set.

Chemiluminescence, is defined as when chemical energy stimulates the emission of a photon, and this includes bioluminescence, as seen in fire flies and many forms of sea life.

Electroluminescence, is when electrical energy or a strong electric field, stimulates the emission of a photon, such as in some lighting applications.

A fluorescence excitation spectrum is when the emission wavelength is fixed and the excitation monochromator wavelength is scanned. In this way, the spectrum gives information about the wavelengths at which a sample will absorb so as to emit at the single emission wavelength chosen for observation. It is analogous to absorbance spectrum, but is a much more sensitive technique in terms of limits of detection and molecular specificity. Excitation spectra are specific to a single emitting wavelength/species as opposed to an absorbance spectrum, which measures all absorbing species in a solution or sample. The emission and excitation spectra for a given fluorophore are mirror images of each other. Typically, the emission spectrum occurs at higher wavelengths (lower energy) than the excitation or absorbance spectrum.

Here are a random sampling of a few common fluorophores that span the UV and Visible range. Some rare earth elements, or lanthanides, have higher electronic orbitals filled, where electrons transition due to metal ligand charge transfers happen between 4f-5d and even 4f-4f orbitals. (Bunzli, 1989) There are many molecules that are luminescent in nature such as a few of the amino acids, chlorophylls, and natural pigments. Others are highly engineered for very specific uses of fluorescence spectroscopy.

Single-Output Fiber BundleThe OSL2FB Single-Output Fiber Bundle has a flexible stainless-steel housing and is a direct replacement for the bundle included with the OSL2 and OSL2IR Light Sources.