Step-index profile

About: Step-index profile is a research topic. Over the lifetime, 3104 publications have been published within this topic receiving 53199 citations.

Optical coupling device

Abstract: An optical mode converter comprises a coupling waveguide (4) and a receiving waveguide (3). The coupling waveguide has at an input end a first effective refractive index n1eff and includes a tapered core (41) of a substantially constant refractive index n1 with a substantially square cross section at the input end (5), having a size that tapers down moving away from the input end. The coupling waveguide has also a cladding (42) at least partially surrounding the tapered core. The receiving waveguide has a second effective refractive index n2eff at an output end and comprises a core (31) of a substantially constant refractive index n2, greater than the refractive index n1 of the tapered core (41) of the coupling waveguide, and a cladding (32) at least partially surrounding the core. A side surface (43) of the tapered core of the coupling waveguide (4) is optically in contact, in a coupling portion, with the receiving waveguide (3) so as to allow optical coupling between the coupling waveguide (4) and the receiving waveguide (3). The refractive index n1 of the tapered core of the coupling waveguide (4) is selected so that the first effective refractive index n1eff and the second effective refractive index n2eff differ from each other in absolute value less than 30% of the difference (n2 - n2eff) between the core refractive index and the effective refractive index of the receiving waveguide (3). A method for fabricating an optical tapered waveguide is also disclosed.

Transverse radiation force in a tailored optical fiber

Abstract: We show, by means of simple model calculations, how a weak laser beam sent though an optical fiber exerts a transverse radiation force if there is an azimuthal asymmetry present in the fiber such that one side has a slightly different refractive index than the other. The refractive index difference {Delta}n needs only to be very low, of order 10{sup -3}, to produce an appreciable transverse displacement of order 10 {mu}m. We argue that the effect has probably already been seen in a recent experiment by W. She et al. [Phys. Rev. Lett. 101, 243601 (2008)], and we discuss the correspondence between these observations and the theory presented. The effect could be used to bend optical fibers in a predictable and controlled manner and we propose that it could be useful for micron-scale devices.

Antireflection film, optical element and optical system

Abstract: An antireflection film includes a multilayer film having six layers, in total, provided between an optical substrate and an adhesion layer. The respective layers of first to sixth layers are laminated in order from one side of the adhesion layer. A refractive index of the antireflection film as a whole is lower than that of the optical substrate and higher than that of the adhesion layer. The first and third layers are low refractive index layers having a refractive index of 1.35 to 1.50 at d line. The second, fourth and sixth layers are middle refractive index layers having a refractive index of 1.55 to 1.85 at the d line. The fifth layer is a high refractive index layer having a refractive index, at the d line, that is in a range of 1.70 to 2.50 and that is higher than that of the middle refractive index layer.

Polymide optical waveguide structures

Abstract: Polyimide optical waveguide structures comprising a core within a cladding wherein at least one of the core and the cladding is a polyimide containing 6FDA; and the complementary portion of the waveguide structure is a polyimide having partial replacement of the 6FDA of the core or cladding composition by BPDA, and wherein the difference in the birefringence of the core and cladding are less than the difference in the refractive index. Copolyimides containing 6FDA and BPDA moieties, and at least one diamine, which have properties useful in optical applications including adjustable refractive index and controllable birefringence, low optical losses, low optical absorbance, increased solvent resistance, and high thermal stability. A method for adjusting the refractive index to make useful copolyimide core/cladding waveguide structures by controlling the 6FDA/BPDA ratio.

Tunable fiber laser based on the refractive index characteristic of MMI effects

Abstract: A tunable erbium-doped all-fiber laser has been demonstrated. This tunable laser is based on a tunable fiber filter using the refractive index characteristics of multimode interference effects. A thinner no-core fiber with a diameter of 104 μm is used to fabricate the tunable fiber filter. The joint point of the thinner no-core fiber with SMF is a taper, which improves its sensitivity for refractive index changes. The filter exhibits a very sensitive response to the change of the environmental refractive index, which is about 1000 nm/RIU in the RI range from 1.418 to 1.427. The tunable fiber laser based on the filter achieved a tunability of 32 nm, with the wavelength tuned from 1532 nm to 1564 nm covering the full C-band. The 3 dB bandwidth of the tunable laser is less than 0.02 nm with the signal-to-noise ratio of about 40 dB.