In many optics applications, it is important to use well-polarized light. However, there are situations in which randomly polarized light has distinct advantages. We demonstrate two approaches by which a polarized light beam can be totally depolarized, each using a simple setup and inexpensive components. The first method, designed for narrow spectrum light, works by combining the horizontal polarization component of the beam with the delayed vertical component. The second method, which is most suitable for broad spectrum light, uses birefringent quartz plates. In both approaches, the polarization state is characterized by Stokes parameters measured using a rotating quarter-wave plate and fixed polarizer. We measure the coherence function of the electric fields and determine the minimum delay or quartz plate thickness required for decoherence. Coherences are modelled by Gaussian or Lorentzian functions and compared with the spectral properties of the light sources.

1.
M.
Bass
,
Handbook of Optics: Volume I
, 3rd ed. (
McGraw-Hill Professional
,
New York
,
2010
).
2.
E. G.
Loewen
,
M.
Nevière
, and
D.
Maystre
, “
Grating efficiency theory as it applies to blazed and holographic gratings
,”
Appl. Opt.
16
,
2711
2721
(
1977
).
3.
B.
Hillerich
and
E.
Weidel
, “
Polarization noise in single mode fibres and its reduction by depolarizers
,”
Opt. Quantum Electron.
15
,
281
287
(
1983
).
4.
B. H.
Billings
, “
A monochromatic depolarizer
,”
J. Opt. Soc. Am.
41
,
966
975
(
1951
).
5.
J. C. G.
de Sande
,
M.
Santarsiero
,
G.
Piquero
, and
F.
Gori
, “
Longitudinal polarization periodicity of unpolarized light passing through a double wedge depolarizer
,”
Opt. Express
20
,
27348
27360
(
2012
).
6.
K.
Takada
,
K.
Okamoto
, and
J.
Noda
, “
New fiber-optic depolarizer
,”
J. Lightwave Technol.
4
,
213
219
(
1986
).
7.
P. G.
Kwiat
,
A. J.
Berglund
,
J. B.
Altepeter
, and
A. G.
White
, “
Experimental verification of decoherence-free subspaces
,”
Science
290
,
498
501
(
2000
).
8.
E.
Hecht
, “
Note on an operational definition of the Stokes parameters
,”
Am. J. Phys.
38
,
1156
1158
(
1970
).
9.
E.
Collet
, “
The description of polarization in classical physics
,”
Am. J. Phys.
36
,
713
725
(
1968
).
10.
H. G.
Berry
,
G.
Gabrielse
, and
A. E.
Livingston
, “
Measurement of the Stokes parameters of light
,”
Appl. Opt.
16
,
3200
3205
(
1977
).
11.
R.
Loudon
,
The Quantum Theory of Light
(
Oxford U. P
.,
New York
,
2000
).
12.
C.
Chatfield
,
The Analysis of Time Series – An Introduction
(
Chapman & Hall/CRC
,
London
,
1989
).
13.
I. R.
Kenyon
,
The Light Fantastic: A Modern Introduction to Classical and Quantum Optics
(
Oxford U. P
.,
New York
,
2011
).
14.
B.
Schaefer
,
E.
Collet
,
R.
Smyth
,
D.
Barret
, and
B.
Fraher
, “
Measuring the Stokes polarization parameters
,”
Am. J. Phys.
75
,
163
168
(
2007
).
15.
S.
Bobach
,
A.
Hidic
,
J. J.
Arlt
, and
A. J.
Hilliard
, “
Note: A portable rotating waveplate polarimeter
,”
Rev. Sci. Instrum.
88
,
036101
(
2017
).
16.
We use here the unit Hz, not the original unit rad/s of the angular velocity. This simplifies comparisons with literature values and data from the spectrometer.
17.
B. E. A.
Saleh
and
M. C.
Teich
,
Fundamentals of Photonics
, 2nd ed. (
Wiley
,
New Jersey
,
2007
).
18.
G.
Ghosh
, “
Dispersion-equation coefficients for the refractive index and birefringence of calcite and quartz crystals
,”
Opt. Commun.
163
,
95
102
(
1999
). See also <https://refractiveindex.info>.
19.
B.-H.
Liu
,
L.
Li
,
Y.-F.
Huang
,
C.-F.
Li
,
G.-C.
Guo
,
E.-M.
Laine
,
H.-P.
Breuer
, and
J.
Piilo
, “
Experimental control of the transition from Markovian to non-Markovian dynamics of open quantum systems
,”
Nat. Phys.
7
,
931
934
(
2011
).
AAPT members receive access to the American Journal of Physics and The Physics Teacher as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.