A zero-mode waveguide is an
optical waveguide
An optical waveguide is a physical structure that guides electromagnetic waves in the optical spectrum. Common types of optical waveguides include optical fiber waveguides, transparent dielectric waveguides made of plastic and glass, liquid ligh ...
that guides light energy into a volume that is small in all dimensions compared to the
wavelength
In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats.
In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...
of the light.
Zero-mode waveguides have been developed for rapid parallel sensing of
zeptolitre sample volumes, as applied to
gene sequencing, by
Pacific Biosciences (previously named Nanofluidics, Inc.)
A waveguide operated at frequencies lower than its
cutoff frequency (wavelengths longer than its
cutoff wavelength) and used as a precision
attenuator is also known as a "waveguide below-cutoff attenuator."
The zero-mode waveguide is made possible by creating circular or rectangular nanoapertures using
focused ion beam on an aluminium layer.
The zero-mode waveguide can also enhance fluorescence signals due to surface plasmons generated at metal-dielectric interfaces. Due to surface plasmon generation field is localized and enhanced as well as it changes the LDOS inside the cavity which leads to increase in Purcell Factor of analyte molecules inside the zero-mode waveguide
The zero-mode waveguide is very useful for Ultraviolet Auto-fluorescence spectroscopy on tryptophan-carrying proteins like beta-galactosidase. With further modification of the zero-mode waveguide with a conical reflector, it is possible to study the dynamic process of smaller proteins like streptavidin with 24 tryptophan.
,
The modified zero-mode waveguide with a conical reflector can be further optimized to enhance the
signal-to-noise ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in deci ...
and reach the ultimate sensitivity of single tryptophan proteins like TNase.
See also
*
Single-molecule real-time sequencing
*
Evanescent field
In electromagnetics, an evanescent field, or evanescent wave, is an oscillating electric and/or magnetic field that does not propagate as an electromagnetic wave but whose energy is spatially concentrated in the vicinity of the source (oscillat ...
References
Biophysics
Physical optics
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