1 Introduction to Laser Micro-to-Nano Manufacturing
17
Fig. 1.10 The guided modes of the dielectric fibers with a variety of diameters. (Reprinted with
permission from [77]. Copyright 2010. Springer Nature)
micrometers to hundreds of micrometers, optical nanofibers enable subwavelength
or even deep subwavelength light guiding, and illustrate merits such as high optical
confinement, strong field enhancement, small size and light weight. High optical
confinement enables optical circuits with tight mode size, low loss sharp bends and
short optical paths, which will be in favor of the minimization and condensing of
optical or photonic devices, and may promote low-threshold or low-power optical
nonlinear effects. Strong field enhancement will offer enhanced light-matter interactions at the nanofiber surroundings, and naturally promote the applications such as
high sensitivity and fast response optical sensing. The steep gradient of the evanescent fields can provide large gradient force for optical trapping or deep potential
wells for cold atom trapping and guiding.
Two mechanisms are mainly involved to realize subwavelength light guiding
in optical nanofibers, high index difference for optical dielectric nanofibers and/or
surface plasmon polaritons for plasmonic fibers.
High Index Difference is commonly utilized to construct optical dielectric
nanofibers which supports optical waveguide modes. Shown in Fig. 1.11, a nanofiber
consist a dielectric core with its refractive index n 1 significant higher than the index
n 2 of the surrounding claddings such as vacuum, air and water. The guided light in
optical dielectric nanofibers obtain the law for the conventional dielectric fibers. The
mode size still contained by the diffraction limit. However, utilizing high-index core
materials and high index difference (n = n 1 −n 2 ) can remarkably reduce the mode
size and extend the optical fibers from micro scale to nano reign. A typical refractive
index difference of an optical nanofiber (n > 2) is obviously higher than that of
commercial optical fiber (n ≈ 0.01).
The waveguiding properties for an optical nanofiber can be deduced from the
Helmholtz equations
17
Fig. 1.10 The guided modes of the dielectric fibers with a variety of diameters. (Reprinted with
permission from [77]. Copyright 2010. Springer Nature)
micrometers to hundreds of micrometers, optical nanofibers enable subwavelength
or even deep subwavelength light guiding, and illustrate merits such as high optical
confinement, strong field enhancement, small size and light weight. High optical
confinement enables optical circuits with tight mode size, low loss sharp bends and
short optical paths, which will be in favor of the minimization and condensing of
optical or photonic devices, and may promote low-threshold or low-power optical
nonlinear effects. Strong field enhancement will offer enhanced light-matter interactions at the nanofiber surroundings, and naturally promote the applications such as
high sensitivity and fast response optical sensing. The steep gradient of the evanescent fields can provide large gradient force for optical trapping or deep potential
wells for cold atom trapping and guiding.
Two mechanisms are mainly involved to realize subwavelength light guiding
in optical nanofibers, high index difference for optical dielectric nanofibers and/or
surface plasmon polaritons for plasmonic fibers.
High Index Difference is commonly utilized to construct optical dielectric
nanofibers which supports optical waveguide modes. Shown in Fig. 1.11, a nanofiber
consist a dielectric core with its refractive index n 1 significant higher than the index
n 2 of the surrounding claddings such as vacuum, air and water. The guided light in
optical dielectric nanofibers obtain the law for the conventional dielectric fibers. The
mode size still contained by the diffraction limit. However, utilizing high-index core
materials and high index difference (n = n 1 −n 2 ) can remarkably reduce the mode
size and extend the optical fibers from micro scale to nano reign. A typical refractive
index difference of an optical nanofiber (n > 2) is obviously higher than that of
commercial optical fiber (n ≈ 0.01).
The waveguiding properties for an optical nanofiber can be deduced from the
Helmholtz equations