Post on 27-Apr-2020
Optics Lab: An overview
List of Experiments • Optical Activity
• Faraday’s Effect • Michelson Interferometer • Ellipsometery • Reflection, Transmission and Fresnel’s coefficients • Interference and Diffraction • Scanning Fabry Perot interferometer • Basic properties of Laser diode • Polarization • Debye Spear’s velocity of sound • Diffraction Grating • Frustrated Total Internal Reflection • Zeeman Effect • Optical Pumping
Reflection, Transmission and Fresnel’s coefficients
•Working with optical components •Investigation of polarization by reflection •Verification of Fresnel’s equations •Finding the Brewster’s angle •Finding the Refractive index of thin micro scope slide
• Drive Fresnel’s Coefficients, rs, ts, rp and tp
• Find the Brewster angle for p- polarized light • Find index of refraction • Predict the reflectance curves by Matlab simulations • Collect the data for Rp, Rs, R45 for all possible incident
angles • Plot data
Experiment
Results
Interference and Diffraction
•Superposition of waves •Interference condition •Fraunhoufer diffraction •Single slit and double slit diffraction patterns •Babinet’s principle: opposite of a slit
Experiment
• Predict the angular dependence of intensity of the diffracted light
where, , a is the slit width and θ is
the angle between the normal to the slit and the distance to the observation point.
• Measure the angular dependence of intensity of diffracted light for different slit widths
• Calculate the width of the central maximum • Do the same for double slit diffraction patterns • Analysis of interference pattern for double slit • Verification of Babinet’s principle
2
2
0)(sin
ββII =
)sin(2
2 θλπβ a
=
azx λ2
0 =∆
CCD/photodiode
θ x
z
sin( )θ =+
xx z2 2
CCD
HeNe
Slit
wid
th ‘a
’
θ
0
10
20
30
40
50
60
70
80
90
100
1 21
41
61
81
101
121
141
161
181
201
221
241
261
281
301
321
341
361
381
401
421
441
461
481 0
20
40
60
80
100
120
1 19
37
55
73
91 1…
12
7 14
5 16
3 18
1 19
9 21
7 2…
2…
271 2…
3…
3…
3…
36
1 3…
3…
415 4…
Single slit diffraction pattern Diffraction pattern of my hair
0
50
100
150
200
250
300 0 18
36
54
72
9…
1…
1…
1…
1…
1…
1…
2…
2…
2…
2…
2…
3…
3…
3…
3…
3…
3…
4…
4…
4…
4…
4…
5…
5…
5…
5…
5…
5…
6…
6…
Interference and diffraction pattern of double slit
Single slit envelope Interference
pattern
Scanning Fabry Perot Interferometer
•To understand the basics of SFPI •To align the instrument to perfection •To investigate the longitudinal modes of HeNe
HeNe Laser
Plano convex lens
Fabry Perot interferometer
Control box
Free spectral range FSR = c/4nd = 1.5 GHz
FWHM=.44ms x calibration factor Finesse (the resolution of the instrument) = FSR/FWHM >150
Basic properties of Laser Diodes
• Laser diode collimation • Understand the concept of PI controller • Use PI controller for tuning of laser diode • Optical spectrum of laser diode
Temperature controller circuit
Current controller
PD LD
Set temperature
IRF540
PI controller
DAQ
TEC element
V
LD temperature
TCLDM9
Tuning of laser diode
Optical power tuning by changing the injection current
Characteristic of Laser diode
Wavelength tuning
Wavelength tuning
Optical power of laser diode reduces with temperature
References
• “Introduction to optics”; Frank L. Pedrotti • “Optics”; Eugene Hecht • www.thorlabs.com
To be continued…..