14.3 Instrumentation
14.3.1 Optical Layout in JASCO CD and CPL Spectrometer
Figure 14.3 shows schematics of the optics for CD and CPL spectroscopy. In a CD
spectrometer, as illustrated in Fig. 14.3a, light from a light source is dispersed by a
monochromator, and is linearly polarized by a polarizer. In contrast, a commercially
available CD spectrometer (e.g., JASCO J-1000 series) is capable of not only
monochromating light but also producing linearly polarized light using a quartz
prism. This linearly polarized light is modulated at a frequency of 50 kHz using a
photo-elastic modulator (PEM) to produce left- and right-handed circularly polarized
light. This circularly polarized light is introduced to a sample, and the difference in
the transmitted left- and right-handed circularly polarized light is measured using a
detector. Figure 14.3b shows a schematic diagram of optics layout in CPL measurements. Light from a light source is first passed through a monochromator, and the
sample is then irradiated by nonpolarized light. The left- and right-handed circularly
polarized fluorescence emitted from the sample is alternately linearly polarized light
at a frequency of 50 kHz using a PEM. A polarizer is placed at the back of the PEM,
and the polarized fluorescence is transmitted synchronously with the modulation of
the PEM, and is passed through a monochromator and then detected by a detector.
The CPL signal corresponds to the difference in fluorescence intensity between leftand right-handed circularly polarized light.
14.3.2 Phase-Sensitive Detection of CD and CPL With
Photo-Elastic Modulator (PEM)
As shown in Fig. 14.4a, a PEM is an optical device consisting of an isotropic optical
material such as quartz, and a piezo actuator. The polarization of the incoming light
PMT
Polarizer
PEM
Sample
Light source
Monochromator
Nonmonochromated
light
Linearly
polarized
light
Circularly
polarized
light
(a)
Light source
Excitation
monochromator Sample
Elliptically
polarized light
Elliptically
polarized light
PEM
Linearly
polarized
light
Polarizer Linearly
polarized
light
Emission
monochromator
PMT
(b)
Nonmonochromated
light
Fig. 14.3 Schematic diagram of optics layouts in CD (a) and CPL (b) measurement principles
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S. Suzuki
14.3.1 Optical Layout in JASCO CD and CPL Spectrometer
Figure 14.3 shows schematics of the optics for CD and CPL spectroscopy. In a CD
spectrometer, as illustrated in Fig. 14.3a, light from a light source is dispersed by a
monochromator, and is linearly polarized by a polarizer. In contrast, a commercially
available CD spectrometer (e.g., JASCO J-1000 series) is capable of not only
monochromating light but also producing linearly polarized light using a quartz
prism. This linearly polarized light is modulated at a frequency of 50 kHz using a
photo-elastic modulator (PEM) to produce left- and right-handed circularly polarized
light. This circularly polarized light is introduced to a sample, and the difference in
the transmitted left- and right-handed circularly polarized light is measured using a
detector. Figure 14.3b shows a schematic diagram of optics layout in CPL measurements. Light from a light source is first passed through a monochromator, and the
sample is then irradiated by nonpolarized light. The left- and right-handed circularly
polarized fluorescence emitted from the sample is alternately linearly polarized light
at a frequency of 50 kHz using a PEM. A polarizer is placed at the back of the PEM,
and the polarized fluorescence is transmitted synchronously with the modulation of
the PEM, and is passed through a monochromator and then detected by a detector.
The CPL signal corresponds to the difference in fluorescence intensity between leftand right-handed circularly polarized light.
14.3.2 Phase-Sensitive Detection of CD and CPL With
Photo-Elastic Modulator (PEM)
As shown in Fig. 14.4a, a PEM is an optical device consisting of an isotropic optical
material such as quartz, and a piezo actuator. The polarization of the incoming light
PMT
Polarizer
PEM
Sample
Light source
Monochromator
Nonmonochromated
light
Linearly
polarized
light
Circularly
polarized
light
(a)
Light source
Excitation
monochromator Sample
Elliptically
polarized light
Elliptically
polarized light
PEM
Linearly
polarized
light
Polarizer Linearly
polarized
light
Emission
monochromator
PMT
(b)
Nonmonochromated
light
Fig. 14.3 Schematic diagram of optics layouts in CD (a) and CPL (b) measurement principles
312
S. Suzuki