Laser Speckle Reducer

STF Series Fiber De-Speckler

Our proprietary De-Speckler technology averages the modal noise within an optical fiber. This reduction in speckle is an ideal choice for fiber assemblies used in the Life Sciences, Digital Laser Projection, Interferometry, Laser Beam Homogenization, Lithography, and Metrology. For many fiber coupled applications, modal noise interferes with optimal performance. We have developed a small, simple and integrated de-speckling system which maximizes performance and reliability in illumination, with no optical loss.

Features and Benefits

Speckle is a random granular pattern commonly observed in the output beam of a laser. It is characterized by many dark and light spots of different intensities visible in a given cross section of the laser beam. This effect occurs as a result of interference between various propagation modes of the light.

The reduction of speckle is important for applications where a homogeneous laser output of uniform intensity is ideal, such as laser-scanning microscopy, flow cytometry, and DNA sequencing. By using the De-Speckler to average the modal noise and greatly reduce speckle, maximized performance can be achieved. Other benefits resulting from speckle reduction can include faster integration times, improved signal-to-noise ratios, and higher throughput.

Our speckle reduction solution has a small form factor and is in-line with a customizable fiber assembly. The fiber size, core shape, jacketing, connectors, and length can all be customized to perfectly suit your application. Please view the product specifications for more information.

This product is popularly paired with our square core fiber and RARe Motheye anti-reflection technology.

Applications

• Life sciences: bioanalytical instrumentation, flow cytometry, gene sequencing, microscopy, spectroscopy

• Digital laser projection

• Interferometry

• Laser beam homogenizers

• Lithography

• Metrology

Specifications

• Power supply: +5 Volts

• Power consumption:  < 1 Watt

• Wavelength range: 400nm – 1550nm

• Fiber core size: 100μm – 400μm

• De-speckling rate: up to 5000 Hz

Customization Options

• Fiber types: all Silica optical fiber; plastic clad fiber; round or square core fiber; RARe Motheye available.

• Jacket types: acrylate, nylon, polyimide, Tefzel

• Assembly types: single fiber assemblies

• Connector types: 905 SMA; 906 SMA; FC/PC; FC/UPC; FC/APC; ST/PC; ST/UPC; ST/APC; cleaved ends; polished ends; round 2.5mm ferrule; custom connectors

STOT Series Laser Speckle Reducer (LSR)

Our laser speckle reducers are nothing other than moving diffusers. But the way they are actuated is absolutely unique. Two innovative technologies are offered, each with its own advantages.

Electro-active Polymer Laser Speckle Reducer (LSR)

With its launch in 2011, we are the first to commercialize electro-active polymers (EAPs) in the field of optics. The basis of this approach is a thin, elastic membrane that carries a lightweight diffuser in its center and four electrodes surrounding it. Actuated at a 90° phase shift, the electrodes induce a circular oscillation of the diffuser in x- and y-direction. The ultra-compact form factor, minimal weight and the absence of noise and vibrations make this technology particularly attractive for hand-held devices.

Reluctance Force Laser Speckle Reducer

Launched in 2016, the reluctance force laser speckle reducer is particularly suitable for applications that require large format glass diffusers. The basis of this approach is a single thin steel structure that is brought into resonance by pulsing an actuating coil with current, which generates a strong reluctance force. Thanks to a high q-factor large amplitudes in the range of 800um are achieved at low power consumption even for heavy glass diffusers.

• Compact

• Silent

• Low power

• Low vibration

Applications

• Head-up displays

• Beam homogenizer

• Metrology

• Microscopy

• Interferometry

• Lithography

Customization

Our laser speckle reducers can be taylored to your specific demands in terms of size, oscillation frequency or transmission range. Tell us your requirements and we will be happy to assess the feasibility.

Laser Speckle Reducer STOT-4C

Our STOT-4C speckle reducer has an aperture of 18.5x18.5mm and is especially suitable for applications where high laser powers and large beam diameters are used. The diffusor is mounted in a thin steel frame. As part of a larger metallic structure the frame is set into motion by the reluctance force, generated by the oscillating magnetic field of a driving coil. If required, the STOT-4C can combine two oscillating diffusors rotated by 90°, realizing optimized despeckling in both directions. The compact driving electronics, assembled on a flexible plastic substrate, stabilizes the resonance frequency in closed-loop mode and includes an error signal.

Mechanical specifications

• Clear aperture: 18.5 x 18.5 mm

• External dimensions (WxHxD): ~40 x 40 x 6mm

• Weight LSR: 11 g

• Weight diffusor: 0.29 g

• Minimal weight for anchor mass: ＞300 g

• Shock test: 500 g

Electrical specifications

• Power supply (micro-USB or solder pads) (1): 3.4 - 5 VDC

• Power consumption (with std. electronics): 50 mW

Optical specifications

• Diffusion angle (FWHM): 8.5 (up to 20 on request)

• Transmission wavelength: 440 – 660 (coated), fused silica (uncoated) nm

• Transmission: ＞ 98 (coated), ＞ 94 (uncoated) %

• Depolarization:  < 0.1 %

• Material: Fused silica

• Coating: High power, double sided

• Damage threshold: ＞ 600 W/cm2

• Oscillation frequency: 120 +/- 10 Hz

• Scratch/dig (2): 60/40

• Oscillation amplitude (peak to peak) minimal / typical / max: 0.6 / 0.8 / 2.0 mm

Thermal specifications

• Storage temperature range: [-40,+85] °C

• Start-up temperature range: [-30,+85] °C

• Operating temperature range at fixed start-up temperature Ts (3):  [Ts-5,Ts+55] °C

Standard products

• LSR-4C-L-18x18-9-T2-VIS: 8.5° diffusion angle, VIS coated

• LSR-4C-L-18x18-9-T2-NC: 8.5° diffusion angle, uncoated

Notes:

• 1 100-230 VAC to 5 VDC micro-USB power supply available

• 2 Over full clear aperture of diffusor

• 3 Outside this temperature range speckle reduction can decrease

Accessories

Bracket kit LSR-4:

• Mounting adapter LSR-4: Required for LSR-4C-LL configuration

• PS-5V-US: 5V DC micro-USB power supply with US plug

• PS-5V-EU: 5V DC micro-USB power supply with EU plug

Assemblies

Please order the following components:

• l  LSR-4C-L (no bracket): 1x LSR-4C, 1x Power supply

• l  LSR-4C-L (with bracket): 1x LSR-4C, 1x Bracket-kit LSR-4, 1x Power supply

• l  LSR-4C-LL (double diffusor configuration with bracket): 2x LSR-4C, 1x Bracket-kit LSR-4; 1x Mounting adapter LSR-4, 2x Power supply

Speckle reduction

Figure 1 (a-c) shows the effect of speckle reduction of the LSR-4C on a laser beam. For all three situations, the intensity distribution and a horizontal line cut is shown. In a), the bare laser beam with a wavelength of 532 nm is shown. The speckle contrast S is 0.27. In b) the LSR is place in the beam path but turned off. The divergence of the beam is increased due to the additional diffusion angle of the 8.5° standard diffusor. The speckle contrast remains almost constant at 0.26. Only when the LSR is turned on, the speckle contrast is significantly reduced by a factor ＞ 4 to 0.06, as one can see in c).

Figure 1: a) shows the intensity distribution of the bare laser beam with a wavelength of 532nm. The speckle contrast C is 0.27. In b) the LSR is placed in the beam path but turned off and the speckle contrast is 0.26. In c) the LSR is oscillating, reducing the speckle contrast to 0.06.

It is important to note that the effect of speckle reduction, quantified by the speckle contrast S, relates to several parameters and is system dependent. The quantity S is defined as the standard deviation from the mean intensity distribution hence a smaller value means less speckle. More information can be found in the general application note about speckle reduction. Our test setup to measure the speckle reduction is presented in Figure 2.

Figure 2: Outline of the speckle reduction test setup. The screen at 45° consists of a white, diffusive surface. The camera takes images of the intensity distribution present on the screen.

Click here for more information on applications of Laser speckle reduction with laser speckle reducer STOT-3000 & STOT-OEM