Laser beam profiling plays an important role in such applications as laser welding, laser focusing, and laser free-space communications. In these applications, laser profiling enables to capture the data needed to evaluate the change in the beam width and determine the details of the instantaneous beam shape, allowing manufacturers to evaluate the position of hot spots in the center of the beam and the changes in the beam�s shape.

Digital wavefront cameras (DWC) with software can be used for measuring laser beam propagation parameters and wavefronts in pulsed and continuous modes, for lasers operating at visible to far-infrared wavelengths:

- beam propagation ratio M�;

- width of the laser beam at waist w₀;

- laser beam divergence angle θ_x, θ_y;

- waist location z-z₀;

- Rayleigh range z_Rx, z_Ry;

- Ellipticity;

- PSF;

- Wavefront;

- Zernike aberration modes.

These parameters allow:

- controlling power density of your laser;

- controlling beam size, shape, uniformity, focus point and divergence;

- aligning delivery optics;

- aligning laser devices to lenses;

- tuning laser amplifiers.

Accurate knowledge of these parameters can strongly affect the laser performance for your application, as they highlight problems in laser beams and what corrections need to be taken to get it right.

Beam Propagation Parameters

M�, or Beam Propagation Ratio, is a value that indicates how close a laser beam is to being a single mode TEM₀₀ beam. This in turn relates to how small a spot a laser can be focused. For a laser beam propagating through space, the equation for the divergence, Θ, of a pure Gaussian TEM₀₀ unfocused beam is given by:

Θ₀₀ = 4λ/πD₀₀                                 (1)

where D₀₀ is the waist diameter of the beam, and λ is the wavelength. Actual beams with additional modes often start with a larger beam waist, D₀, and/or have a faster divergence Θ₀. In this case Equation (1) becomes:

Θ₀ = M² 4λ/πD₀                               (2)

where Θ₀ and D₀ are the divergence and width of a higher mode beam and M� is greater than 1 and is named the �Beam Propagation Ratio� per the ISO 11146 standard. When a pure Gaussian laser beam is focused, the diameter of the focused spot is defined by:

d₀₀ = 4λf /πD₀₀                                 (3)

where D₀₀ is the ideal focused spot diameter,  f is the focal length of the lens, and is placed one focal length from the lens as shown in the Figure 1. However, when a distorted or multimode beam is focused, Equation (3) becomes:

d₀ = M² 4λf  / πD₀                                (4)

Apart from M�, the measured beam propagation parameters characterizing laser beams are:

w₀ = d₀/2� the waist radius in X (horizontal) and Y (vertical) directions;

z-z₀ � the distance between measurement and waist planes;

z_R � the Rayleigh range, for which the radius of curvature R of the wavefront is minimal;

θ � the divergence angle of the measured laser beam far from the waist;

     R � the radius of curvature of the wavefront in the measurement plane.

STPV Series All-in-One Laser Beam Analyzers

High Resolution CCD Beam Profiler

Instant Beam Propagation & Wavefront Analysis

One Shot M² Measurement

The smart all-in-one compact digital wavefront camera (DWC) beam profiler performs beam propagation analysis in one shot.

Thanks to its capability to measure simultaneously intensity and phase data at ultra high resolution, beam shape and intensity distribution can be measured at any distance from its original location without moving parts. All critical parameters for laser beam monitoring such as energy distribution and beam propagation parameters can be measured without need of purchasing additional tools.

DWC combined with laser beam measurement software provides comprehensive one-shot measurements of the laser beam: beam propagation parameters such as M�, divergence, tilt, energy characteristics in any XY plane.

Users can make necessary adjustments in real time by visualizing the beam along the Z propagation axis, graph of waist, 2D/3D intensity profiles can be easily extracted by selecting a Z position with a slider.

Principle

Propagation parameters are measured by DWC on real beams by focusing the beam with a fixed position lens of known focal length, and then measuring the characteristics of the artificially created beam waist and divergence.

Measurement of the beam propagation parameters with DWC is based on the simultaneous measurement of the high-resolution images of intensity and wavefront. The wavefront is computed starting from two slightly defocused beam intensity images acquired on one CCD camera inside DWC by mathematical computations involving the two images and the difference between them (Figure 2). From the wavefront, the beam propagation parameters are obtained by straightforward but tedious computations.

Typical Applications

1. Laser Beam & Wavefront Profiling

Featuring resolution of 250 000 measurement points, high dynamic range (� 1500 λ of wave tilt at 633 nm), and real time wavefront analysis at 25Hz video frame rate, DWC is an ideal tool for laser beam analysis.

Multiple views of the reconstructed high resolution wavefront, containing 3D plot, wavefront gradient, fringes display are output in real time.

For laser beam measurement, the technique uses Digital Wavefront Sensor to obtain high-resolution intensity and wavefront images of the propagating beam at one location on a 1M pixel CCD array camera. From the one-shot intensity and phase measurements and numeric propagation the laser beam is obtained at >10 positions. The instrument is suitable for measurement of both CW and pulsed lasers down to single-shot rates, and provides quantitative measurement of numerous beam spatial characteristics in accordance with the ISO 13694 standard and M² parameters according to the ISO 11146 standard. Beam diameters are obtained with accuracy to better than 2% that translates to M² measurements with accuracy to better than 4%.

2. Beam Propagation Analysis

DWC is a one shot device offering detailed beam propagation analysis in a range up to several Rayleigh distances in the beam propagation direction.

Without displacing the device, the beam's energy - related characteristics such as beam celtroid and peak locations, and peak fluences can be precisely and quickly computed by purely numerical procedures, in a desired number of planes around the position of DWC.

The quality of the laser beam and the visualization of its hot spots can be monitored with no operator intervention over large distances around the laser beam waist.

3. Beam shaping & beam monitoring

DWC can be used for precise beam monitoring & beam shaping - both in intensity and in phase - made e.g. by phase spatial light modulators (SLM's), deformable mirrors (DM's) and other beam shaping and beam forming devices.

DWC is used e.g. to control of the adjustment of beam shaping modules to generate round and square top hat focal spots, offering ultimate resolution, speed and dynamic range.

Key Advantages

• Wavefront sensor, beam propagation parameters & power measurement in one device

• High spatial resolution for both intensity and wavefront measurements

• One shot M� measurement without additional accessories or moving parts

• Instant beam propagation analysis, power measurement in any plane

• Laser beam monitoring with real time display of intensity, wavefront, PSF

• Compact & light beam profiler for pulsed & CW lasers

• Custom solutions for UV, NIR & FIR wavelength range

Measurement Capabilities

• Beam M�

• Propagation parameters

• Beam energy parameters in any plane

• Beam Wavefront Measurement

• CW & Pulsed Lasers

Parameters

• Entrance aperture: 5.9 x 3.1 mm

• Z separation: 17.5 mm

• Measurement points: 500 x 500

• Absolute accuracy: <0.01λ

• Sensitivity: <0.005λ

• Repeatability: <0.01λ rms

• Dynamic range: 500λ

• Acquisition rate: 15 Hz max (processor dependent)

• M2 accuracy: �5%

• M2 repeatability <2%

• λ range: 350 - 1100 nm (Silicon CCD) <350 & >1100 nm with other cameras

Software Functions

GUI software XP, Vista and Windows 7 compatible, performs intensity and wavefront acquisition in a remarkably fast and easy way and provides comprehensive tools for beam profiling including intensity distribution and beam propagation parameters.

1. Acquisition & Display

- Automatic calibration & acquisition

- Live display 2D and 3D intensity, wavefront, PSF Single and continuous acquisition

2. Analysis

Beam intensity parameters:

- Maximum intensity levels

- Ellipticity of the beam spot

- Beam spot major and minor axis dimensions

Beam propagation parameters:

- M2 parameter for the X and Y directions

- Waist size in X and Y directions

- Distance between sensor position and waist planes

- Rayleigh range

- Divergence angle of the beam

- PSF, Strehl ratio

- Real-time Zernike display and analysis

- Profiles of wavefront and intensity

3. Export & Report

-- Wavefront and Zernike data Report Editor, HTML Compatible Presentation

VIS/NIR Beam Profiler: STCam CCD

Our CCD is developed to provide excellent sensitivity from the VIS to NIR spectral range. Thanks to its high resolution and its small pixel size, the STCam is a high performance tool for laser beam analysis of continuous wave (CW) and pulsed laser modes. Due to its high dynamic range the STCam captures even higher laser modes with outstanding detail.

The passive cooled sensor of the STCam is constructed without cover glass to avoid interference patterns. For sensor protection a low distortion neutral density filter is integrated. The STCam supports the ultra-fast FireWire IEEE 1394b interface with data transfer rates up to 800 Mbit/s. The plug and play

design facilitates easy and flexible integration and operation.

The portable STCam is designed to be used in a variety of applications in industry, science, research and development, including:

l         Laser beam analysis of CW and pulsed lasers,

l         Quick control of laser modes and adjustment errors,

l         Test equipment for scientific research,

l         Near-Field and Far-Field analyses of lasers, LED devices and other light sources.

The enhancement of product quality, process reliability and efficiency are just a few of the many benefits of our unique beam profiler cameras. The STCam includes the specifically designed analysis software, STRayCi, which supports Windows XP/Vista operating systems. Its sophisticated software architecture opens up new opportunities in laser beam analysis according to ISO standards.

The concept of the STCam enables easy adaption to standard optical imaging systems, attenuators and opto-mechanical components ensuring highest flexibility. This includes:

l         Microscope lens and beam expander,

l         UV-Converter and IR-Converter,

l         Fixed and variable attenuators, etc.

ACCESSORIES

Neutral Density Filter: To expand the power range of the STCam several absorptive and metallic-coated neutral density filters are available, which are specified by optical densities ranging from OD 1.0 to OD 4.0.

FireWire Component: We offer different FireWire PCI / PCI Express cards for installation direct into the PC. Standard FireWire cables are suitable for industrial applications and are available in various lengths.

Trigger Device: To synchronize the STCam with pulsed laser systems, our trigger device is perfectly suited. This frequency and delay generator is software controllable and enables the synchronization of up to four beam profilers with different delay times simultaneously.

* without condensation

.

Neutral Density Filter

Our neutral density filters allow broadband attenuation for a spectral range from VIS to NIR. Due to their excellent surface quality the absorptive and reflective filters enable precise beam attenuation for low power applications. The level of attenuation is specified by the optical density. Filters with different optical densities can be combined. A filter adapter is available to mount the filters on the STCam aperture.

CO2 Laser Beam Profiler

The high performance STCL system is based on industry�s unique imaging technique. It is designed for monitoring high-power CO2 lasers in best performance. Thanks to its high resolution and its incomparable real-time capabilities, this highly efficient beam profiler is optimized for laser beam analysis of continuous wave (CW) and pulsed laser systems. The STCL system ensures beam profiling:

l         By high frame rates and high resolution,

l         Without optical components in the beam path,

l         Without scanning techniques, fluorescent materials or toxic fumes through acrylic mode burns.

The STCL supports the ultra-fast FireWire IEEE 1394a/b interface with data transfer rates up to 800 Mbit/s. The plug and play design facilitates easy and flexible integration and operation.

The compact and portable STCL is designed to be used in a variety of applications in industry, science, research and development, including:

l         Laser beam analysis of CW and pulsed lasers,

l         Quick control of laser modes and adjustment errors,

l         Test equipment for scientific research,

l         Near-Field and Far-Field analyses of lasers.

The enhancement of product quality, process reliability and efficiency are just a few of the many benefits of our unique beam profiling system.

The STCL system includes the specifically designed analysis software, STRayCi, which supports Windows XP/Vista operating systems. Its sophisticated software architecture opens up new opportunities in laser beam analysis according to ISO standards.

ACCESSORIES:

Attenuation Units: The water-cooled attenuation units are based on zinc selenide (ZnSe) and are designed for a 10� / 45� angle of incidence. Due to its excellent performance the unit can be used up to laser powers of 3kW and intensities of 5kW/cm2.

FireWire Components: We offer different FireWire PCI/PCI Express cards for installation direct into the PC. Standard FireWire cables are suitable for industrial applications and are available in various lengths.

Trigger Device: To synchronize the STCL system with pulsed laser systems, our trigger device is perfectly suited. This frequency and delay generator is software controllable and enables the synchronization of up to four beam profilers with different delay times simultaneously. 

Technical Specifications:

* different parameters on request

** without condensation

Laser Beam Profiling Software STRayCi

Our sophisticated beam profilers are available with the specifically designed analysis software, STRayCi, which supports Windows XP/Vista operating systems. It is available as 32 Bit / 64 Bit version and can control up to eight beam profiler cameras on a single computer.

Due to its clearly designed menu structure, STRayCi shows self-explanatory functions, which help the user to access quickly standard settings. Incomparable visualization modes, extensive analytical capabilities as well as new developed correction algorithms ensure the highest accuracy in laser beam analysis.

A wide range of beam width techniques e.g. 2nd Moment, Knife Edge, Moving Slit, Plateau, Gauss-Fit can be applied to determine quick and reliable standard beam parameters. The unique measurement tool enables the continuous monitoring of beam parameters, beam position and power density distribution. Helpful features like AOI Tracking, AOI Optimization, Zoom Functions, Look-Up Tables, etc.

simplify the laser beam analysis.

The extraordinary graphical and analytical tool of STRayCi can be used for live data (LiveMode) and stored data (SaveMode) simultaneously, while each mode has its own individual functions. This makes STRayCi the most advanced analysis software on the market.

STRayCi is equipped with flexible data and image output capabilities. This permits the user to store data and images in the format that is compatible with their needs.

A clearly arranged and printable protocol view displays the chosen measurement parameters as well as the most important laser beam analysis results.

STRayCi is compatible with guidelines of the international standard organization for laser beam measurements:

l         ISO 11145: Vocabularies and symbols

l         ISO 11146: Beam width, propagation ratio,�

l         ISO 11670: Beam positional stability,�

l         ISO 13694: Beam power density distribution,�

STRayCi works only with a USB software protection lock. It is a hardware based security solutions to protect and encrypt the software against piracy.

MINIMUM SYSTEM REQUIREMENTS:

l         Windows XP / Vista

l         Pentium IV / AMD Processor

l         128 MB graphic card, Open GL V1.4 compatible

l         100 MB free memory

l         PCI / PCIe slot for FireWire card

l         USB port for dongle connection

l         CD / DVD-ROM drive for software installation

l         Internet access for update request

STRayCi Special Features

REAL-TIME BEAM PROFILING

2D / 3D intensity plots / Cross sections / Histogram

Pointing stability (x-y fluctuation, COG- position analysis, ect.)

Parameter stability (intensity, power, center x-y, beam size)

Parameter results (beam statistics, beam width, beam parameter)

CAMERA CONTROL

Multiple camera support

Different measure types

User-selectable exposure time and gain factor, auto-exposure time

Floating average and variable brightness

ANALYSIS FUNCTIONS

Beam statistics (power, max intensity, COG, etc.)

Beam width (2nd Moment, Gauss / Super-Gauss-Fits, Plateau, Knife Edge, Moving Slit, ect.)

Beam parameter (beam width, ellipticity, uniformity, etc.)

CALIBRATION AND CORRECTION TOOL

Background subtraction, auto-background

Pixel correction technology (offset correction, linearity, etc.)

Power calibration

OTHER FEATURES

User-defined Area of Interest (AOI)

AOI tracking and optimization

Color palettes incl. auto-contrast function

Zoom functions

2D profile arithmetic operations, filters, transformations, etc.

E-mail support

FLEXIBLE OUTPUT

Data: txt, tiff

Image: jpeg, png, bmp, gif, tiff

Protocol: pdf

  STBQM Series Beam Profile Analyses

1. STBQM-10 Beam Profile Analysis

The STBQM10 laser beam profiler is a high precision, CCD based beam profiler for use with lasers with wavelengths between 190 and 1100 nm. Allied with our powerful but intuitive software package, the BQM10 makes quick and accurate characterization of your lasers a reality.

The high quality 12-bit CCD array gives excellent resolution. Features include USB2.0 interface means portability and ease of use, RJ45 GPI/O connector for control of synchronization of lighting and 32MB onboard memory for frame buffering. Thus, the STBQM10 can be easily transferred to different laptop or desktop computers. The user interface is simple and intuitive but with many useful features.

Specifications:

• Parameters of ISO 11146 series of standards

• �� format CCD 1392x1040 array with 4.65um square pixels

• 12-bit digitization � 60dB dynamic range

• No frame grabber required (32MB RAM on-board memory)

• USB2.0 direct connection with no external power supply required

• Compact (45x45x56mm) and lightweight (130grams)

• 15 fps at 1392x1040, 30 fps at 640x480

• Measures both CW and pulsed beams

• Second-moment and Gaussian fit

• ~3% beam diameter accuracy

The STBQM10 laser beam profiler comes with the following

�   Optical head

�   User software on CD

�   Cables

�   User manual

Options -

Wavelength range - 350nm to 1100nm

Accessories -

STBQM - 100      Variable attenuator

STBQM - 110      Set of 6 ND filters, screw mount

STBQM - 120      Beam pick off

2. STBQM-10 Beam Profile Analysis

The BQM-50 is designed to allow complete measurement laser beam propagation characteristics. In this system a liquid lens, which can vary its optical power in response to a changing input voltage, is used to remove the need for the translation stage used in traditional systems to allow beam widths to be sampled through the laser beam caustic. This makes the BQM-50 one of the most compact and capable beam quality systems available.

Features:

�          Measures M�, Divergence angle, Width at waist, Waist location, Rayleigh

�          Range and Astigmatism etc.

�          NPL Technology Applied

�          Measurement time under 20 seconds

�          Compact (150mm L x 50mm Dia.) and Portable

�          Easy alignment and adjustment

�          Compatible with CW and Quasi-CW Pulsed Laser source

This system was developed in conjunction with NPL and is protected by an NPL patent. The clear, simple to use software gives total control over the measurement which can be aligned and completed in a few minutes.

Specifications:

Ordering information

STBQM-50:

Automated beam propagation analyzer system for laser wavelengths between 400nm and             1100nm. System includes optical unit, CCD camera, cables, software, and user manual.

Optional accessories

STBQM-100 Attenuator wheel with 5 ND filters (range nominally from ND0.5 to 5.0)

STBQM-110 Set of 5 ND filters, screw mount (range nominally from ND0.5 to 5.0)

STBQM-120 Beam pick off, 1-10% of an incident beam

STBQM-130 Beam splitter, 1-10% of an incident beam

STBQM-200 Beam dump, 50W maximum, air cooled

STBQM-400 Beam expander, 5X

STBQM-410 Beam reducer, 5X

STBP Laser Beam Profiler

The Laser Beam Profiler provides high resolution real-time monitoring and quantitative characterization of spatial beam intensity distributions. Primarily designed for excimer lasers, it may be utilized for all pulsed or CW lasers as well as for incoherent sources, covering an extremely wide spectral range from NIR to soft X-rays. The UV/EUV sensitivity is achieved by a quantum conversion coating on the CCD chip. 

A variety of different sensor types (large/small area, highest spatial resolution, sensitivity and dynamic range) are available and can be adapted to specific applications. The software supports also periphery devices like adaptive mirrors, stepper motors, attenuators, shutters or power monitors. Automated or remote-controlled measurements are facilitated by the help of a powerful macro language.

The applications comprise:

-          Determination of beam parameters according to ISO 11146

-          Diagnosis of pointing stability (ISO 11670)

-          Pulse-to-pulse fluctuations

-          Beam propagation analysis (caustic measurement)

-          Characterization of beam shape (uniformity, steepness) according to ISO 13694 (especially for homogenized beams)

-          On-line laser beam inspection (e.g. recognition of �hot spots�)

-          Optimizing of laser operational parameters

-          Alignment of optical components

Special Features:

-          Wide spectral range: 1064 � 13nm

-          Small and large area CCD sensors

-          USB 2.0 interface (ideal for laptop)

-          High dynamic range (12/14 bit)

Applications:

-          Beam diagnostics (NIR, Vis, UV, EUV)

-          ISO beam parameters

-          Beam propagation/focusability

-          M²  (caustic measurement)

STBC Laser Beam Characterization

Beam Parameters

Quantitative determination of all relevant laser beam parameters from the acquired profiles is achieved with the help of the comprehensive beam characterization software �MrBeam�, which makes use of standard ISO evaluation procedures.

Beam parameters according to ISO standards:

• Beam width 2^nd moment (ISO 11146)

• Divergence, M² (with caustic setup; ISO 11146)

• Pointing stability (ISO 11670)

• Beam shape/uniformity (ISO 13694)

Software:

• Various acquisition modes: �grab�, �averaging�, �floating average�

• Evaluation of beam parameters: beam width (2^nd moment, centroid, ellipticity, uniformity, relative pulse energy, pointing stability etc.

• 2D profile arithmetics (ADD, SUB, MULT, DIV etc.)

• Selection of area-of-interest for analytic beam evaluations

• Real-time display and evaluation of cross-sections, 3D graphics

• Profile-fit (Gaussian, super-Gaussian, top-hat etc.)

• Colour palettes incl. Analytic functions (e.g. �intensity threshold�)

• Easy-to-use �zoom�-functions

• Comprehensive user-programmable macro language

• Export of all data and profiles

The system includes:

-          Digital camera (USB 2.0 interface for note-book or PC)

-          Beam analysis software

Optional extensions:

-          Translation stage (e.g. for caustic measurement)

-          Hartmann-Shack wavefront sensor

-          Adaptive mirror for closed-loop beam stabilization

Trigger/delay generator