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OXP-08 Optical Gratings

  Topics:
Grating Constant
Amplitude-, Phase Grating
Reflection-, Transmission Grating
Ruled-, Holographic Grating
Spectral Resolution
Diffraction Order

Joseph von Fraunhofer
1787 - 1826

 


Joseph von Fraunhofer, the investigator of the solar lines, invented the diffraction grating in 1821. This optical element showed a much higher dispersion than any glass prism and allowed Fraunhofer to investigate the solar spectrum in a resolution much better than ever seen before.
Enormous quality improvement as well as optimization of the manufacturing technique of ruled gratings are the results of Henry Rowlands efforts in development of diffraction gratings. His gratings were used worldwide and were unbeaten in quality and resolution for decades. Nowadays holographic techniques using the interference of laser beams allow manufacturing gratings with larger grating constants and bigger size.
In this experiment, transmission gratings of different grating constants are investigated. By knowing the grating parameter, the wavelengths of light sources can be determined. A light source with known wavelength is used to characterize a specific grating. On a spectral apparatus the wavelengths of spectral lines are measured and the resolution power of gratings is demonstrated. Finally, a two-dimensional grating is not only used to produce impressive patterns of light spots, but gives an idea about the principles of x-ray diffraction on crystal lattices or atomic layers.


 

 


 

Examples of Investigation and Measurement


Wavelength of a laser
By using a grating with known grating constant the wavelength of a laser is determined. Through this result gratings with unknown parameters are investigated.

Spectrum of a light source
The diffraction of a line spectrum by a grating is performed. For higher diffraction orders the advantage of a larger spread of the spectrum and therefore a higher resolution is demonstrated. On the other hand the drawback of overlapping spectra in higher orders can be shown in this experiment.

Spectral resolution
In combination with a magnifying lens the lines of a spectral lamp are magnified. By varying para meters like grating constants or magnification their influence on the resolution of the apparatus can be determined and discussed.

Two-dimensional grating
The effect of a two-dimensional grating is shown on two crossed line gratings. The relations of the grating to the diffracted light pattern are demonstrated by twisting the two gratings or by using gratings with different grating constant.
 


 

 

 

 

OXP-08   Required Equipment


1  
1


02.0200
02.0300

 


Profile rail OCM 650, 200 mm
Profile rail OCM 650, 300 mm

The high precision optical rails are made out of special anodized aluminum. The rails are the base for various modules attached to carriers.
 




 

1

02.1022

Carrier OCM 650, 20 mm with screen holder

This module can mount optical screens. Through the attached carrier, the screen holder can be placed onto the optical rail. The carrier 20 mm and the holder are made out of special anodized aluminum.
 

1

02.1602

 

Screen with scale

Experimental results like colour spectra and interference patterns can be visualized on these screens. Horizontal or vertical scales allow calibrations and quantitative measurements; a screen with an aperture is used for observing back-reflected rays. The screens are made out of anodized aluminum plates with one side painted white and can be fixed onto screen holders (02.1022, 02.1608).
 

2

02.2126
02.2150

Mounting plate OCM 650 for click 25, including carrier 20 mm
Mounting plate OCM 650 for click 50, including carrier 20 mm

Mounting plates are used to hold optical mounts. A characteristic feature of the mounting plates is the “click” mechanism of the inserts based on spring loaded spheres. Snapping in the groove of the inserted click mount, the optical element is kept in an exact position. On the other hand, the system allows a quick and easy change of the mounted inserts.
The mounting plates are made out of special anodized aluminum. Mounted onto the carrier 20 mm, the mounting plates can be placed onto an optical rail.
 

1

02.6106

4 axis adjustment holder KH650, theta, phi, X and Y, including carrier 20 mm

This adjustment holder mounts a Diode Laser or an LED lamp. Using the fine pitch adjustment screws, the optical axis can be aligned within the range of 3 mm. For fine alignment of the angle of the light beam, two additional pitch adjustment screws are attached onto the back of the holder. The holder and the carrier 20 mm are made out of special anodized aluminum and can be placed onto an optical rail.
 

1 04.0054
04.0061

Biconvex lens f=150 mm, mounted in click 50 mount
Plano convex lens f=40, mounted in click 25 mount

Different glass lenses are mounted onto a special anodized aluminum click mount 25 mm by two threaded mounting rings to be used in connection with a mounting plate (02.2126).
 

  05.0106

Spectral lamp with slit and power supply

This unit consists of a light source emitting descrete spectral lines in the visible range.The lamp in its housing is made out of special anodized aluminum fixed onto a mounting plate and can be placed onto an optical rail. The front aperture of the housing is a slit with 1 mm width, which is very helpful in spectrally resolving setups. The lamp is connected to a main switch unit with the following properties:

voltage: 230 VAC / 50 Hz
case dimensions: 200 mm x 160 mm x 62 mm
The spectral lamp provides the main lines at the following wavelengths:

Line                                 Length
red line                        at 615 nm
yellow line                    at 578 nm
green line                     at 546 nm
turquoise line                at 492 nm
blue line                       at 436 nm
purple line                    at 405 nm
 




1

05.0226

DIMO diode laser module, 532 nm (green)

Due to its collimated beam, this frequency doubled green YAG laser is an ideal light source for experiments dealing with ray tracing and beam propagation. The diode in its 40 mm x 25 mm diameter housing tube made out of special anodized aluminum can be fixed onto a four axis adjustment holder and can be aligned to the optical axis. Driven by the LDD-05 active power supply (07.0206), the output power is controlled in the range from 0 to 3 mW.

1 07.0010

BNC – Banana adapter connection leads 2x4 mm plugs

This BNC cable is used to connect a photodetector (07.0101) to a digital multimeter (19.0400).
Total length: 1 m
 

1 07.0102

PIN Si Photodetector BPX 61 complete with housing

Using a BNC cable, the photodetector can be connected to a measuring device. Mounted onto a special anodized aluminum click 25 head, the photodetector is to be used in connection with a mounting plate (02.2126).
 

1 07.0206

LDD-05 active power supply

The universal LDD-05 active power supply is used for all laser and LED light sources. It recognizes which source is connected and sets the parameters for it automatically. The unit is equipped with a main switch, a regulation knob for adjusting the laser or LED power and a safety lock. The provided USB bus interface allows control through a personal computer or laptop and qualifies this unit as multimedia source.
The housing is made out of shock-proof plastic with an aluminum front and rear panel.

Voltage: 230 VAC / 50 Hz
Case dimensions: 200 mm x 160 mm x 62 mm.
 




1 09.1746

Beam expander magnification 6x

The beam expander, consisting of two lenses mounted onto a click 25 optical mount and a 40 mm x 25 mm diameter sleeve, can be fixed onto the mounting plate (02.2126) which is attached to the optical rail using a carrier. The divergence of the magnified beam is adjusted by varying the telescope length.
 


1 09.1810

Optical grating assembly

A hinged joint angle connector holds various optical gratings of 50 mm x 50 mm x 2,5 mm provided in this assembly to study the diffraction of gratings. The unit can be mounted onto two optical rails which can be set in a defined angle to each other. By adjusting the hinge angle, the beam deviation angle can be measured on a scale from -90 - +90° at intervals of 2°.

The set of five optical gratings consists of:

1 Grating 80 l/mm
1 Grating 100 l/mm
1 Grating 300 l/mm
1 Grating 600 l/mm
1 Grating 1200 l/mm

The metal parts are made out of special anodized aluminum.
 

1 09.1848

Beam expander magnification 2.7x

The beam expander, consisting of two lenses mounted onto a click 25 optical mount and a 40 mm x 25 mm diameter sleeve, can be fixed onto the mounting plate (02.2126) which is attached to the optical rail using a carrier. The divergence of the magnified beam is adjusted by varying the telescope length.
 

1 19.0400

Digital multimeter 3 ˝ digits

he digital multimeter is used for relative intensity measurements of light beams. It has to be connected to a photodetector via banana adapter connection leads.

Specifications:

Display LCD, 3 ˝ digits  
AC voltage ranges 2 / 20 / 200 / 750 V
Frequency range 40 - 400 Hz
DC voltage ranges 0,2 / 2 / 20 / 200 / 1000 V
AC current ranges 2 / 20 / 200 mA / 20 A
Frequency range 40 - 400 Hz
DC current ranges 0,2 / 2 / 20 / 200 mA / 20 A
Resistance ranges 0,2 / 2 / 20k / 0,2 / 2 / 20 MΩ.







 


 


 




 

 

Experiments

OXP-01 Refraction of Light

OXP-02 Prisms

OXP-03 Lenses

OXP-04 Reflection & Transmission

OXP-05 Beam Bending

OXP-06 Refractometer

OXP-07 Diffraction of Light

OXP-08 Optical Gratings

OXP-09 Spectral Analysis

OXP-10 Interference

OXP-11 Interferometer

OXP-12 Holography

OXP-13 Polarisation

OXP-14 Double Refraction

OXP-15 Colour Mixing

OXP-16 Optical Filters

OXP-17 Absorption & Emission

OXP-18 Image Projection

OXP-19 Camera

OXP-20 LED & Laser Diode

 

Kits

Basic Kit

Complete Kit

Advanced Kit