This document summarizes a student's lab experiment on the effect of changing the incident angle on the optical properties of a distributed Bragg reflector (DBR). The student created DBR stacks with different materials and analyzed the reflection at incident angles of 0, 30, 45, and 89 degrees. The results showed that reflection increases as the incident angle increases. Specifically, reflection was lowest at 0 degrees and highest at 89 degrees. In conclusion, changing the incident angle alters the output of the DBR by increasing reflectivity.

1. To study the effect of change in
incident angle on the optical
properties of a DBR
Presented by:
Muzammil Khan
Department of Electronic Engineering, BUITEMS

2. Contents
 Motivation
 Introduction
 Methodology
 Results & discussion
 Conclusion
 References

3. Motivation
 Distributed Bragg reflector(DBR) used to make the partially reflected mirrors which
have broad applications in optics. DBR are also used as waveguide in fibre optics.
DBR are being used in interferometers which are then being used in spectroscopy.
 DBR used in formation of optical filters which are tunable over a wide bandwidth
and can be used to pass or reflect the desired amount of light or to focus the light
of desired wavelengths.
 This lab purpose is to learn broad prospective of the DBR and to provide the
insight to the different optical properties of it.

4. Introduction
 DBR (Distributed Bragg Reflector) is a reflector which is formed by the multiple
layers of different materials of varying refractive index and produce the partially
reflected mirrors. The properties of material such that material thickness or
refractive index or the gap between the respective layers can be varied depending
upon the applications of DBR mirrors. DBR provide high reflectivity and finite
absorption as well.

5. Methodology
 Create a new project in “Open filter” software.
 Then add filter in it and select the range of the central wavelength upto 550nm.
 Then create stack formula in a filter. Use (HL) for single and (HL)^2 for 2 layers.
 Took dielectric material SiO2 and air whose refractive index is 1.42 and 1.
 The symbol “H” is used for SiO2 and “L” for air respectively.
 Then click on analyse and calculate reflection, as well as changing the incident
angle start from zero, 30 degree, 45 degree and 90 degree.

6. Results & Discussion
 Results showed below tells us about the comparison of reflection at different
incident angle used in DBR.
 Through this we can say that changing the incident angle will makes the reflectivity
wider.
 When 2 pair of SiO2 and air used and central wave length is 550 nm and incident
angle is 0 degree the results becomes.

7. Results & Discussion
When 2 pair of SiO2 and air used and central wave length is 550 nm and
incident angle is 45 degree the results becomes
When 2 pair of SiO2 and air used and central wave length is 550 nm and incident angle
is 30 degree the results becomes

8. Results & Discussion
When 2 pair of SiO2 and air used and central wave length is 550 nm and
incident angle is 89 degree the results becomes
In last when all the results are combined is show that how the
reflection increases with the change in incident angle.

9. Conclusion
 From this lab we concluded that as the incident angle is changing from 0 degree to
89degree the reflectivity increases.
 changing the incident angle will change the output of DBR.
 90 degree is parallel with DBR so light don’t pass through DBR and no result is
shown means no reflectivity with 90 degree

10. References
 Lab lectures by DR. Anayat.
 Optical effects in solids book by David B. Tanner.

11. THANKS