Telecommunication Wavelength Region Research Articles

Broadband Near-Infrared Emission from TransparentNi2+-Doped Sodium Aluminosilicate Glass Ceramics

Broadband near-infrared emission from transparent Ni2+-dopedsodium aluminosilicate glass-ceramics is observed. The broad emissionis centred at 1290 nm and covers the whole telecommunication wavelengthregion (1100–1700 nm) with full width at half maximum of about 340 nm.The observed infrared emission could be attributed to the 3T2(F)→3A2(F) transition of octahedral Ni2+ ions thatoccupy high-field sites in nanocrystals. The product of the lifetime andthe stimulated emission cross section is 2.15×10−24 cm2s.It is suggested that Ni2+-doped sodium aluminosilicate glassceramics have potential applications in tunable broadband light sourcesand broadband amplifiers.

Ultrafast Optical Responsive SWNT/Polymer Thin Films in Guided Wave Mode Geometry

AbstractSingle walled carbon nanotubes (SWNT) having good optical and electrochemical properties were solublized by aromatic polymers. The polymer‐wrapped SWNT film cast from solution showed transient bleaching with a time constant of recovery less than 1 ps in both the visible and optical telecommunication wavelength region. Polymer thin film containing SWNT was assembled into the guided wave mode geometry with a low refractive index polymer.

Rigorous reflectance performance analysis of Si3N4 self-suspended subwavelength gratings

In this paper, we make an investigation into the reflectance performance of the Si3N4 self-suspended subwavelength grating (SSG) via changing several parameters including the incident wavelength, the grating period, the grating thickness and the grating filling ratio. For TM polarization of incidence, numerical results by the rigorous coupled-wave method reveal that the reflectance spectrum of the Si3N4 SSG has a narrow linewidth (less than 1nm), high peak reflectance (100%), and low side bands (less than 0.5%) simultaneously in the optical telecommunication wavelength region. By using a micro-electromechanical-systems actuator, it is believed that the Si3N4 SSG should serve as tunable optical filters in optical telecommunication systems.

Bismuth-doped zinc aluminosilicate glasses and glass-ceramics with ultra-broadband infrared luminescence

Broadband infrared luminescence covering the optical telecommunication wavelength region of O, E and S bands was observed from bismuth-doped zinc aluminosilicate glasses and glass-ceramics. The spectroscopic properties of the glasses and glass-ceramics depend on the thermal-treatment history. With the appearance of gahnite (ZnAl 2O 4) crystalline phase, the fluorescent peak moves to longer wavelength, but the fluorescent intensity decreases. The ∼1300 nm fluorescence with a FWHM larger than 250 nm and a lifetime longer than 600 μs possesses these optical materials with potential applications in laser devices and broadband amplifiers. The broad infrared luminescence from the bismuth-doped zinc aluminosilicate glasses and glass-ceramics might be from BiO or bismuth clusters rather than from Bi 5+ and Bi 3+.

Omnidirectional mirror coating design for infrared applications

An omnidirectional mirror, with a reflectance ( R) of 99.5% for all angles of incidence and both polarisations, was designed from quasi-periodic dielectric stacks based on Fibonacci sequence (FS) by selecting appropriate materials for high and low refractive index layers. At R = 99.5%, the initial omnidirectional spectral range was found to be from 1437 to 1618 nm, which covers completely the telecommunications wavelength region and the S, C and L bands of the erbium doped fiber amplifier gain region. The individual layers within the FS have the same physical thickness, thus having non quarter-wave optical thickness at the centre wavelength. Optimisation from the initial design can expand the omnidirectional spectral region at R = 99.5%, as well as show a higher value of R over the initial omnidirectional spectral range. Deposition and characterisation of the mirror coating have taken place using microwave assisted direct current magnetron sputtering and various characterisation techniques.

GeO 2: Bi, M (M = Ga, B) glasses with super-wide infrared luminescence

Broadband infrared luminescence covering the optical telecommunication wavelength region of O, E and S bands was observed in GeO 2: Bi, M (M = Ga, B) glasses prepared by conventional melting–quenching technique. The luminescence with a maximum at around 1320 nm possesses a full width at half maximum larger than 300 nm and mean fluorescent lifetime longer than 500 μs when excited by an 808 nm-laser. These glasses may have potential applications in widely tunable laser and super-broadband optical amplifier for the optical communications.

Ultrafast optical switching at the telecommunication wavelength by single electron transfer between fluorene-containing redox polymer and its counter anion

Ultrafast and large absorption change in the optical telecommunication wavelength region was achieved in solid films by making transitory expansion of a π-electronic system with photoinduced electron transfer and reverse reactions between redox-active ion pairs. Femtosecond dynamics of absorption changes at about 500–1550 nm due to single electron transfer was studied for a poly(tetramethyleneoxide) film containing 2,7-bis(4-pyridiniumyl)fluorene unit as part of the main chain. It showed ON response in less than 100 fs and fastest OFF response in 240 fs at the telecommunication wavelength. This polymer film may be applied to tetrahertz all optical information processing in the telecommunication system.

Large Spectral Birefringence in Photoaddressable Polymer Films

A photoaddressable azobenzene-side-chain polymer (see Figure) optimized to exhibit a large optical birefringence of Δn = 0.5 at 650 nm is described. The birefringence extends well into the telecommunication wavelength region, which, together with the high optical transparency above 650 nm, promises applications for integrated photonic device applications. The writing dynamics of the polymer are examined, and it is shown that the rewriteability is limited by photobleaching.

Thermally induced holographic gratings in liquid crystals at telecommunications wavelengths

The formation of holographic gratings in nematic liquid crystals by laser beams in the telecommunications wavelength region around 1500 nm through a thermal mechanism has been demonstrated. The gratings have been observed in a four-wave mixing experiment with millisecond-long writing pulses in 5CB liquid crystal. The relatively low absorption of the crystal was compensated by the absorption in the coating of the experimental cell wall. Optimization of the liquid crystal temperature near the phase transition point allowed a diffraction efficiency of about 1% to be reached. Holographic liquid crystal devices can be used in all-optical switching, beam routing, automatic wavefront correction, phase conjugation, etc.

Two-step K(+)-Na+ and Ag(+)-Na+ ion-exchanged glass waveguides for C-band applications.

A two-step K(+)-Na+ and Ag(+)-Na+ ion-exchange technique is introduced to fabricate single-mode channel waveguides in BK7 glass for the telecom-wavelength region. The dependencies of insertion loss, polarization-dependent loss (PDL), end bending loss of curved waveguides on channel width, diffusion time, and annealing time are investigated. Results show that postannealing is a required process for improving waveguide properties and an optimal annealing time exists. Although relatively narrow mask openings are used in most one-step ion-exchange processes, a wider channel width, to as wide as 10 microm, is preferred for this two-step method. The minimum coupling loss to/from single-mode fiber and the propagation loss is found to be 0.4 dB and 0.3 dB/cm, respectively. For 5-cm-long waveguides the PDL is less than 0.1 dB. For the S-bend structure the cosine curve exhibit apparently a lower bending loss than the double-arc curve.

Tunable optical filter for wavelength division multiplexing using dynamic interband photorefractive gratings

We demonstrate a narrow-bandwidth tunable optical filter in the telecommunication wavelength region near 1550 nm using dynamic holography. A thick holographic reflection grating is produced in a pure potassium niobate crystal with interband photorefractive effects. The filter is tuned by changing the grating spacing by means of an acousto-optic deflector. High wavelength selectivity with a 3 dB channel bandwidth of 0.13 nm is achieved. Tuning times are in the order of a few hundred microseconds.

Concentration Dependence of Emission Properties of Tm3+-Doped Tellurite Glasses in Telecommunication Wavelength Region.

Concentration dependence of emission properties and lifetimes of Tm3+ doped tellurite glasses in telecommunication wavelength region were investigated. According to Judd-Ofelt analysis, it was clarified that the quantum efficiency of 1.46μm in Tm3+-doped tellurite glasses was almost equal to that in fluoride glasses, which were used as host materials for Tm3+-doped fiber amplifiers (TDFA). The emission intensity ratio of the 1.80μm band to the 1.46μm band increased with increasing Tm3+ content. Moreover, the lifetimes of the 3H4 level decreased rapidly with increasing Tm3+ content. These results show that tellurite glass is useful as host materials of TDFA and in order to achieve a high quantum efficiency of 1.46μm emission in tellurite glasses, the concentration of Tm3+ should be low so that cross relaxation can be suppressed.

Single-photon counters in the telecom wavelength region of 1550 nm for quantum information processing

Single-photon counters in the telecom wavelength region of 1550 nm for quantum information processing

Single-photon counters in the telecom wavelength region of 1550 nm for quantum information processing

We describe the status of commercially available InGaAs InP avalanche photodiodes for use as single-photon counters in the telecom wavelength region of 1550 nm.

A single-photon counter for long-haul telecom

Quite a few groups have turned their attention to using commercially available InGaAs/InP APDs, originally developed for optical communication applications, as SPADs for photon counting at 1300 nm and 1550 nm. This research has turned out to be quite fruitful, and there are many applications emerging in optical metrology (optical time-domain reflectometry) in eye-safe range finding and in future quantum technologies, where databits are encoded on individual photons. This article describes the status of these commercially available InGaAs/InP APDs used as single-photon counters in the telecom wavelength region of 1550 nm.