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Modular Multi-Port Integrating Spheres
Interchangeable Port Inserts for Modular Faces
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4P4 Sphere Major Design Features
Thorlabs' Modular Integrating Spheres each provide a durable, highly reflective surface to optimally diffuse light. The sphere is constructed inside a cuboctahedral (fourteen-sided) housing that can be configured for a wide variety of applications. Each of the eight triangular faces can support a Ø5 mm port with SM1 internal threads, enabling easy mounting of our mounted photodiodes or fiber-coupled components such as LEDs or spectrometers (SM1 adapters may be needed). Either three or four of the square faces can be configured with inserts selected by the user as described in the Modularity section below. The two faces that are not modular provide a universal 8-32 / M4 tapped hole, allowing mounting to the 25 mm rail system stand (included with stock items) or a Ø1" post. These integrating spheres are available from stock as one of two pre-set configurations or ordered as a custom configuration using the tool below.
The spheres are manufactured from PTFE-based bulk material that has high reflectance in the 250 - 2500 nm wavelength range (see Specs tab) and is resistant to heat, humidity, and high levels of radiation. This reflective surface is designed to have specific roughness and diffusive reflection properties and should not be cleaned using solvents, as this could damage the inner surface. We only recommend using compressed air for cleaning the inner surfaces of the integrating spheres.
Integrating spheres enable high sensitivity measurements of optical signals in a variety of setups. An integrating sphere causes the incoming radiation to undergo multiple reflections over the sphere surface, which diffuses and depolarizes the light beam. This makes it the ideal instrument for many applications such as laser power, flux, reflectance and radiance measurements, as well as creating a uniform light source for camera calibration.
Any of the inserts in the modular faces can be swapped for other interchangeable port inserts, including additional inserts sold separately below. The inserts are each fastened by two M3 screws; to exchange the included inserts with other inserts, loosen the screws using a 2 mm (5/64") hex key or balldriver. Custom inserts may be available for applications not served by the inserts available from stock. Contact Tech Support for more information.
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Integrating Sphere Material Reflectance
Ultraviolet and Blue Fluorescence Emitted by Integrating Spheres
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Typical yields at each wavelength are around four orders of magnitude lower than the excitation wavelength. 
The spectral fluorescence yield relates the intensity of the fluorescence emitted within the integrating sphere with the intensity of the excitation wavelength. The yield is calculated by dividing the wavelength-dependent, total fluorescence excited over the entire interior surface of the sphere by the intensity of the light excitation.
Data were kindly provided by Dr. Ping-Shine Shaw, Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
A material of choice for coating the light-diffusing cavities of integrating spheres is polytetrafluoroethylene (PTFE). This material, which is white in appearance, is favored for reasons including its high, flat reflectance over a wide range of wavelengths (see the Specs tab for details) and chemical inertness. However, it should be noted that integrating spheres coated with PTFE emit low levels of ultraviolet (UV) and blue fluorescence when irradiated by UV light. Spheres coated with barium sulfate, which is an alternative coating with lower reflectance, also fluoresce in this wavelength range. [1-3]
Hydrocarbons in the Coatings Fluoresce
Fluorescence Wavelength Bands and Strength
The UV and blue fluorescence from PTFE is primarily excited by incident wavelengths in a 200 nm to 300 nm absorption band. The fluorescence is emitted in the 250 nm to 400 nm wavelength range, as shown by the figure to the right. These data indicate that increasing the excitation wavelength decreases the fluorescence emitted at lower wavelengths and changes the shape of the fluorescence spectrum.
As the levels of hydrocarbon contaminants in the PTFE increase, fluorescence increases. A related effect is a decrease of the light output by the integrating sphere over the absorption band wavelengths, due to more light from this spectral region being absorbed. [1, 3]
Impact on Applications
Minimizing Fluorescence Effects
Since the history of each integrating sphere's exposure to hydrocarbon contaminants is unique, it is not possible to predict the response of a particular sphere to incident radiation. When an application is negatively impacted by the fluorescence, calibration of the integrating sphere is recommended. In , the authors describe a calibration procedure that requires a light source with a well-known spectrum that extends across the wavelength region of interest, such as a deuterium lamp or synchrotron radiation, a monochromator, a detector, and the integrating sphere.
The 4P3 sphere is pre-configured for light measurement, designed so that the sphere is continuous opposite the Ø1" port that would be used for a light source. This reduces the probability of primary reflections occurring on a seam around a port plug.
These spheres are shipped pre-mounted to the included rail system stand with M4 cap screws. To unmount the sphere, the screws can be removed using a 3 mm hex key or balldriver. The interchangeable port inserts are each fastened by two M3 screws; to exchange the default inserts with other inserts, loosen the screws using a 2 mm (5/64") hex key or balldriver.
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Interior Side of 4P13 Insert
These easily interchangeable port inserts are designed for use with Thorlabs Ø100 mm Modular Integrating Spheres. Two included M3 screws secure each insert to the sphere, allowing the insert of any modular face to be swapped out using a 2 mm (5/64") hex ball driver. The sphere-facing sides of the 4P10, 4P11, and 4P13 inserts have the same radius of curvature and are engineered with the same highly reflective bulk material as the rest of the sphere, minimizing losses from changes in geometry. The 4P12 insert does not have any bulk material in its design as the aperture is closely matched with the hole in the integrating sphere for the modular face.
Dust caps are included with the 4P11 and 4P13 inserts to protect the sphere from dust and debris when not in use, while the 4P12 insert should be exchanged with a 4P10 port plug insert for the same purpose. However, ports closed with caps or left open will disrupt the uniform reflectance properties of the sphere. Prior to operation of the sphere, any unused, open port insert should be exchanged for a 4P10 insert for optimal performance.
If the inserts available from stock are not suitable for your application, please contact Tech Support to inquire about custom inserts.
Use the tool below to configure a custom integrating sphere. The number of modular faces and fixed Ø5 mm ports selected through this tool are permanent structures that cannot be modified after purchase. Port inserts chosen for each of the modular faces are interchangeable by the user.