Light-induced Self-written Research Articles

Multimode near-infrared light-induced self-written optical waveguides for optical soldering

Connecting optical components in a highly precisely aligned manner that avoids significant losses due to misalignment is an important objective for future light-based high-speed data transmission technologies. We fabricated multimode light-induced self-written (LISW) optical waveguides using near-infrared (NIR) light for multimode optical component self-coupling. Multimode optical fibers were optically soldered with NIR light (≤ 1 mW) using this waveguide, with an insertion loss of only 0.69 dB observed when soldered at 0.6 mW.

Flexible light-induced self-written optical waveguide with 50 μm core size

We demonstrate a NIR light-induced self-written (LISW) optical waveguide between graded-index (GI) glass optical fibers with a 50 μm core size (50GIFs) using gel material. We describe the optical properties of the LISW optical solder in terms of its flexibility, adhesiveness, and loss. The results demonstrate that the two 50GIFs were self-coupled through the LISW optical waveguide, and the connection maintained adhesiveness against displacement. A low loss and relaxation of alignment tolerance were demonstrated for the optical interconnection between two 50GIFs using flexible LISW optical soldering. This technology is applicable to future autonomous driving systems using high-speed optical data transmission.

All‐Solid Near‐Infrared Light‐Induced Self‐Written Optical Waveguides and Optical Self‐Coupling

In recent datacenters, considerable data communication has been performed between servers and storages; therefore, an optical interconnection with a wider band is required. Silicon photonics has attracted attention as a technology that places optical engines closer to switch application‐specific integrated circuits and realizes broadband optical interconnection. To utilize silicon photonics, it is necessary to overcome high‐precision alignment between silicon waveguides and single‐mode fibers (SMFs) having vastly different mode field diameters. Optical self‐coupling using light‐induced self‐written (LISW) optical waveguide technology is a potential solution. Previously, near‐infrared (NIR) LISW optical waveguides are fabricated using an SMF with an approximate 10 μm core through irradiation with 10 μW NIR light (1310 and 1550 nm). However, the cladding is liquid, which motivates to fabricate all‐solid LISW optical waveguides. In this study, all‐solid NIR LISW optical waveguides are produced using a core‐selective polymerization method, and single‐mode LISW optical self‐coupling between two SMFs is realized. To enhance the performance of the waveguides, additional resins are incorporated into the high‐refractive‐index base monomer during the cladding formation process. Through the experimentation, the potential for achieving even greater loss reduction by optimizing the hybridization between the base monomer and the supplementary resins is demonstrated.

Flexible Light-Induced Self-Written Optical Waveguide Using Gel Material

For in-vehicle optical communication systems, an air gap exists between two plastic optical fibers (POFs) to avoid damage to the POF end due to vibrations. There exists the disadvantage that a loss occurs in air gaps. To solve the issue of high-loss optical coupling, in this study, we designed a light-induced self-written (LISW) optical waveguide between POFs using gel material. It was demonstrated that the two optical fibers were automatically interconnected through the LISW optical waveguide, and the connection maintained the adhesiveness against mechanical displacement.

Near-Infrared Self-Written Optical Waveguides for Fiber-to-Chip Self-Coupling

The light-induced self-written (LISW) waveguide technique is a promising candidate for the practical realization of a passive alignment between telecommunication and silicon photonic devices. While silicon is transparent to wavelengths above 1100 nm, the one-photon polymerization wavelength range is limited below 1100 nm. In this study, LISW waveguide fabrication at telecommunication wavelengths was demonstrated using a single-photon photopolymerizing resin. The LISW waveguide fabrication threshold values are lower than that of the two-photon photopolymerization system by six to seven orders of magnitude. LISW waveguides are fabricated from a single-mode fiber, a vertical-cavity surface-emitting laser, and a silicon waveguide. Using this technique, fiber-to-chip self-coupling between silicon photonic devices at telecommunication wavelengths is demonstrated. The results demonstrate the potential of the LISW technique for optical self-coupling of telecommunication and silicon photonic devices.

Two-Photon Absorption Light-Induced Self-Written Waveguide for Single-Mode Optical Interconnection

We propose two-photon absorption light-induced self-written (LISW) waveguide formation using short-wavelength infrared pulse laser light. It is suitable and efficient for single-mode optical interconnection, and also promising for small-core single-mode optical interconnection. The approach offers the possibility of not only decreasing the insertion loss, but also reducing the interconnection task time. We assessed this approach for single-mode optical interconnection. We obtained an LISW waveguide loss of about 0.06 dB for an LISW waveguide length of 100 μ m and a connection loss per facet of about 0.37 dB. We also presented the results on the interconnection between high-numerical-aperture small-core thermally-diffused expanded-core single-mode fibers having the mode field diameters of about 3 μ m by using the same approach. The results showed the present approach to be a promising alternative route for efficient interconnection of small-core single-mode optical devices, such as silicon nanowires with appropriate configurations.

Light-induced self-written waveguide fabrication using 1550 nm laser light.

Light-induced self-written (LISW) optical waveguides were fabricated for the first time, to the best of our knowledge, using a photopolymerizable resin system formed by 1550nm pulse laser light. A two-photon absorption (TPA) chromophore with a TPA cross section of several hundred Goeppert-Mayer (GM) at 1550nm was used. Furthermore, the optical interconnection between a single-mode fiber and a fiber Bragg grating was demonstrated by the present technique, using one-way irradiation of 1550nm laser light through the single-mode fiber. The LISW waveguide formation using 1550nm laser light offers a new and promising alternative route for optical interconnection in silicon photonics technology.

Light induced self-written waveguides interactions in photopolymer media.

We present experimental and theoretical study of the interaction of Light Induced Self-Written (LISW) waveguides in photopolymers. We show that the diffusion of the monomer controls the refractive index distribution. Consequently it influences the interaction between the LISW channels allowing the observation of anti-crossing behavior or the propagation of an array of non interacting LISW waveguides.

Electro-optic phase modulation in light induced self-written waveguides propagated in a 5CB doped photopolymer

We present the inscription of a Light Induced Self-Written (LISW) waveguide in a 4-cyano-4'-pentylbipheny (5CB) doped photopolymer. The dynamic reorientation of the 5CB molecules in the material under applied electric field leads to birefringence in LISW waveguide and thus allows the control of the phase of the guided mode.

Serially grafted polymer optical waveguides fabricated by light-induced self-written waveguide technique

Serially grafted polymer optical waveguides were fabricated by the light-induced self-written (LISW) waveguide technique for the first time to our knowledge. To realize functional waveguide cores by the LISW technique, transparent materials at the writing wavelength were selected. By inserting thin transparent partitions, a serial-graft structure consisting of passive and active waveguides without any misalignment was realized automatically. This technique is advantageous for its extremely easy process over conventional fabrication techniques.

Light-Induced Self-Written Optical Waveguides

Light-induced self-written (LISW) technology is a unique and simple method of forming low-loss 3-dimensional (3-D) optical circuits in photopolymers using radiation from an optical fiber. Since this technology is applicable to almost all kinds of optical fiber and optical wiring, many studies have been carried in a number of different organizations on the applications of this technology. The technology helps simplify optical interconnections, and it is expected that it will reduce the cost of mounting optical devices. In this paper, we introduce LISW technology and report on related studies developed in our research group.

Light-Induced Self-Written Polymeric Optical Waveguides for Single-Mode Propagation and for Optical Interconnections

Light-induced self-written (LISW) polymeric optical waveguides were fabricated in a photopolymerizing resin mixture solution using a single-mode optical fiber. In order to realize a straight waveguide core, a pre-UV treatment was performed before core formation. Single-mode propagation of laser light at 1310 nm was realized by appropriately controlling the ratio of the resins in the mixture for the first time. Moreover, optical interconnection between two single-mode fibers was demonstrated based on this technology.

New Fabrication Method of Self-written Waveguide by Using Photosensitive Polyimide

A Photosensitive polyimide (PSPI) precursor for light-induced self-written (LISW) waveguide based on a poly(amic acid) (PAA) and 1,4-dihydropyridine derivatives (DHP)s has been developed. The PAA was prepared by ring-opening polyaddition of aromatic fluorinated tetracarboxylic dianhydrides and diamines. Upon exposing the PSPI precursor to laser light, a self-focusing effect induced by the difference in refractive index between the exposed and unexposed portions was observed. Thermal treatment of the laser exposed PSPI precursor gave a polyimide LISW wave guide with no other processing steps. The coupling loss between two multimode fibers with a 0.5 mm gap, was decreased from 5.2 dB in air to 0.7 dB by insertion of the PSPI LISW waveguide. This simple new fabrication method of LISW waveguide structures allows convenient and easy alignment of optical waveguide components.

Waveguide shape control and loss properties of light-induced self-written (LISW) optical waveguides

We show the feasibility of automatic waveguide formation by means of the self-trapping effect of multimode optical fiber irradiation into a photopolymerizing resin. By using a graded-index multimode optical fiber, we experimentally obtained a straight waveguide of over 20 mm in length. It is shown that its growth properties, such as waveguide shape and diameter, depend on the propagation modal distribution along the optical fiber used for the waveguide formation. Moreover, an all-solid polymer optical waveguide that relies on the selective photopolymerization proceeding into the photopolymerizing resin mixture is also demonstrated. We call this type of waveguide a light-induced self-written optical waveguide. The measured propagation loss in the waveguide is 1.0 dB/cm or less for the wavelength range 0.8/spl sim/1.0 /spl mu/m. The proposed technology is capable of eliminating both costly lenses and the need for an alignment system from optical waveguide devices.