Glass Channel Waveguides Research Articles

Bending Loss Analysis of Chalcogenide Glass Channel Waveguides for Mid-Infrared Astrophotonic Devices

In this study, the bending losses of chalcogenide glass channel optical waveguides consisting of an As2Se3 core and an As2S3 lower cladding layer were numerically evaluated across the astronomical N-band, which is the mid-infrared spectral range between the 8 µm and 12 µm wavelengths. The results reveal the design rules for bent waveguides in mid-infrared astrophotonic devices.

Characterisation of Channel Waveguides Fabricated in an Er3+-Doped Tellurite Glass Using Two Ion Beam Techniques

Two methods were proposed and implemented for the fabrication of channel waveguides in an Er-doped Tellurite glass. In the first method, channel waveguides were fabricated by implanting 1.5 MeV and 3.5 MeV energy N+ ions through a special silicon mask to the glass sample at various fluences. Those waveguides implanted at a fluence of 1.0 × 1016 ions/cm2 operated up to 980 nm, and showed green upconversion of the Erbium ions. In the second method, channel waveguides were directly written in the Er3+: TeO2W2O3 glass using an 11 MeV C4+ ion microbeam with fluences in the range of 1 · 1014–5 · 1016 ions/cm2. The waveguides worked in single mode regime up to the 1540 nm telecom wavelength. Propagation losses were reduced from the 14 dB/cm of the as-irradiated waveguides by stepwise thermal annealing to 1.5 dB/cm at λ = 1400 nm.

FORMATION OF CRYSTALLINE LINES OF LITHIUM HEPTAGERMANATE IN LITHIUM GERMANATE GLASS

In this study, direct femtosecond laser writing of continuous crystalline lines possessing oriented structure and formed by ferroelectric Li2Ge7O15 phase in the bulk of glass of molar composition, mol. %: (20 Li2O; 80 GeO2). The unexpected difference between crystalline phases precipitating in glass under the laser beam and during the heat-treatment is revealed. The obtained results are of interest for the development of crystalline channel waveguides in lithium germanate glass.

On-chip supercontinuum generation in nanostructured Ge11.5As24Se64.5 chalcogenide waveguides using Panda-ring resonator

The on-chip scale microring circuit is proposed to numerically investigate the supercontinuum (SC) generation of light power. The device is formed by the chalcogenide Panda-ring resonator with the nanoscale planar waveguide using Ge11.5As24Se64.5chalcogenide glass channel waveguide, air-clad and MgF2glass for lower cladding. The waveguide is designed to exhibit normal dispersion along with a low-energy pumped at 1.55 μm using a short pulse, which has the duration of 50 fs and peak power ranging from 1 W to 100 W. The numerical result obtained has shown a good-quality SC generation of both the spectral bandwidth and high output peak power. All SC spectral extended to more than 13 μm by cumulative Kerr nonlinearities. The obtained results can be useful for developing new experimental work in the important area of SC generation on compact chip broadband sources, which can be used in both infrared and radio wave applications.

Ge22As20Se58 glass ultrafast laser inscribed waveguides for mid-IR integrated optics

Ultrafast laser inscription has been used to produce channel waveguides in Ge22As20Se58 glass (GASIR-1, Umicore N.V). The mode field diameter and waveguide losses at 2.94 μm were measured along with the waveguide dispersion in the 1 to 4.5 μm range, which is used to estimate the zero-dispersion wavelength. Z-scan measurements of bulk samples have also been performed to determine the nonlinear refractive index. Finally, mid-IR supercontinuum generation has been shown when pumping the waveguides with femtosecond pulses centered at 4.6 μm. Supercontinuum spanning approximately 4 μm from 2.5 to 6.5 μm was measured which, to the best of the authors’ knowledge, represents the broadest and the deepest IR supercontinuum from an ultrafast laser inscribed waveguide to date. This work, combined with the long wavelength transmission of GASIR-1 up to 15 μm, paves the way for realizing further ultrafast laser inscribed waveguide devices in GASIR-1 for mid-IR integrated optics applications.

Design and optimization of As2S5 chalcogenide channel waveguide for coherent mid-infrared supercontinuum generation

We numerically demonstrate mid-infrared supercontinuum generation in dispersion-engineered chalcogenide glass channel waveguide. The proposed ridge waveguide consists of arsenic pentasulfide (As2S5) strip deposited on magnesium fluoride (MgF2) substrate and air acting as an upper cladding. The structure parameters are calculated and optimized by using the fully vectorial finite-difference in the frequency-domain (FDFD) method Results indicates that the proposed waveguide exhibits an all normal dispersion (ANDi) profile over a wide spectral range with a zero dispersion wavelength (ZDW) around 2μm. By solving the generalized nonlinear Schrödinger equation, we demonstrate supercontinuum generation extending from the near infrared to the mid infrared region. Indeed, a broad and perfectly coherent ultra-flat supercontinuum spectrum spanning the region from 700 to 5200nm is successfully generated by using a 25kW peak power 100fs input pulse pumped at 2.5μm, in a waveguide of 5mm length.

Nd^3+-doped ion-exchanged aluminum germanate glass channel waveguide

K+–Na+ ion-exchanged channel waveguide has been fabricated in Nd3+ doped aluminum germanate (NMAG) glasses with potential photosensitive property. The channel waveguide exhibits single mode at 1.3μm and the mode field diameters were measured to be horizontally 10.1μm and vertically 5.3μm, respectively. Amplified spontaneous emissions (ASE) of 905, 1060, 1334 and 1816nm originating from the 4F3/2 level were recorded under ~800nm diode laser pumping and the maximum stimulated emission cross-sections for the 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions are derived to be 21.5 × 10−21 and 7.6 × 10−21cm2, respectively. In addition, with 71.8% quantum efficiency and the largest emission intensity among various Nd3+ doping cases, 2wt% Nd2O3 is considered as the optimized doping concentration for the compact channel waveguide. The ion-exchanged Nd3+-doped NMAG glass channel waveguides offer favorable prospects for the development of optical waveguide amplifiers, broadband light sources and infrared UV-written grating waveguide lasers.

Fabrication of optical channel waveguides in crystals and glasses using macro- and micro ion beams

Active and passive optical waveguides are fundamental elements in modern telecommunications systems. A great number of optical crystals and glasses were identified and are used as good optoelectronic materials. However, fabrication of waveguides in some of those materials remains still a challenging task due to their susceptibility to mechanical or chemical damages during processing. Researches were initiated on ion beam fabrication of optical waveguides in tellurite glasses. Channel waveguides were written in Er:TeO2–WO3 glass through a special silicon mask using 1.5MeV N+ irradiation. This method was improved by increasing N+ energy to 3.5MeV to achieve confinement at the 1550nm wavelength, too. An alternative method, direct writing of the channel waveguides in the tellurite glass using focussed beams of 6–11MeV C3+ and C5+ and 5MeV N3+, has also been developed. Channel waveguides were fabricated in undoped eulytine-(Bi4Ge3O12) and sillenite type (Bi12GeO20) bismuth germanate crystals using both a special silicon mask and a thick SU8 photoresist mask and 3.5MeV N+ irradiation. The waveguides were studied by phase contrast and interference microscopy and micro Raman spectroscopy. Guiding properties were checked by the end fire method.

Ion-exchanged Tm^3+:glass channel waveguide laser

Continuous wave laser action around 1.9 μm has been demonstrated in a Tm(3+)-doped germanate glass channel waveguide laser fabricated by ion-exchange. Laser action was observed with an absorbed power threshold of only 44 mW and a slope efficiency of up to 6.8% was achieved. Propagation loss at the lasing wavelength was measured to be 0.3 dB/cm. We believe this to be the first ion-exchanged Tm(3+)-doped glass waveguide laser.

Eu3+ and Sm3+ co-activated aluminum germanate glass channel waveguide as irradiation source for photodynamic therapy

A bright and compact orangish-red fluorescence trace is observed in an Eu3+/Sm3+ co-doped K+Na+ ion-exchanged aluminum germanate (NMAG) glass channel waveguide under excitation with a 488nm Ar+ laser. The excitation wavelength range and the emission intensity of Eu3+ in NMAG glass are remarkably improved by the sensitization of Sm3+, and the energy transfer probability and efficiency are calculated to be 151.2s−1 and 25.3%, respectively. Meanwhile, the energy transferred from Sm3+ can be efficiently utilized to generate intense fluorescence of Eu3+ due to the large spontaneous emission probabilities of the Eu3+: 5D0→7FJ (J=1, 2, and 4) transitions that reach up to 68.9, 364.7, and 152.6s−1, respectively. Enhanced fluorescence in the Eu3+/Sm3+-doped NMAG glass channel waveguide, which matches the excitation band of most photosensitizers, holds great promise for photodynamic therapy.

White upconversion luminescence in Tm3+/Ho3+/Yb3+ triply doped K+–Na+ ion-exchanged aluminum germanate glass channel waveguide

Rare-earth ions doped K+–Na+ ion-exchanged aluminum germanate (NMAG) glass channel waveguides have been designed and fabricated. Under 980nm laser pumping, an intense upconversion white light transmission trace was observed in Tm3+/Ho3+/Yb3+ triply doped NMAG glass channel waveguide and a high-brightness light spot was achieved from the output end of the fiber connected to the waveguide channel. The fluorescent colors were diverse and located within or near the white region in CIE chromaticity diagram under various pumping powers. These admirable results indicate that Tm3+/Ho3+/Yb3+ triply doped NMAG channel waveguide is a promising light source for medical and high-precision processing illumination.

Diode-pumped femtosecond solid-state waveguide laser with a 49 GHz pulse repetition rate

We report on the first demonstration of a passively mode-locked, diode-pumped, monolithic Yb:glass channel waveguide laser that incorporates a semiconductor saturable absorber mirror. Stable and self-starting mode-locking is achieved in a Fabry-Perot cavity configuration producing a pulse repetition rate up to 4.9 GHz. The shortest pulse duration of 740 fs is generated with 30 mW of average output power at a center wavelength of 1058 nm. A maximum output power of 81 mW is produced during mode-locking with corresponding pulse duration of 800 fs.

Optical amplification of Pr^3+-doped ZBLA channel waveguides for visible Laser emission

We report on the first observation of optical signal amplification in the visible range into praseodymium doped ZBLA glass channel waveguides obtained by ion exchange. Up to 30% signal amplification was obtained at 639 nm. This result shows the potential of rare earth doped fluoride glasses in the form of channel waveguides for integrated solid state visible laser sources.

Sm^3+-doped germanate glass channel waveguide as light source for minimally invasive photodynamic therapy surgery

In Sm(3+)-doped K(+)-Na(+) ion-exchanged aluminum germanate (NMAG) glass channel waveguide, a clear and compact red amplified spontaneous emission (ASE) trace is observed under the excitation of a 488nm Ar(+) laser. 78% photons of ASE fluorescence in visible region are demonstrated to be located in 600-730nm wavelength range. High-directivity and high-brightness ASE fluorescence of Sm(3+)-doped NMAG glass channel waveguide, which matches the excitation band of most photosensitizers (PS) currently used in photodynamic therapy (PDT) or clinical trials, has promising potential application as an excitation light source for PDT treatment.

Formation of slab waveguides in eulytine type BGO and CaF2 crystals by implantation of MeV nitrogen ions

Ion implantation, compared with other waveguide fabrication methods, has some unique advantages. It has proved to be a universal technique for producing waveguides in most optical materials. The authors of the present article reported fabrication of channel and slab waveguides in an Erbium-doped tungsten tellurite glass by implantation of MeV energy N+ ions. The present article reports successful adaptation of the same technique to the fabrication of slab waveguides in eulytine type bismuth germanate (BGO) and CaF2 crystals. This is the first report on successful waveguide fabrication in these materials using 3.5MeVN+ ions at implanted fluences between 5×1015 and 4×1016ions/cm2. Spectroscopic ellipsometric measurements revealed the existence of guiding structures in both materials. M-line spectroscopic measurements indicated guiding effect in the as-implanted BGO up to 1550nm and up to 980nm in the as-implanted CaF2. Ion implantation induced the appearance of three peaks in the UV/Vis absorption spectrum of CaF2, that can be attributed to colour centres.

Fluoride and oxyfluoride glasses for optical applications

This paper present some recent developments on fluoride and oxyfluoride glasses, including glass composition, basic characterizations, technology and prospects, especially the development of rare earth doped fluoride glass channel waveguides for applications requiring integrated optical components. New Heavy Metal Fluoride Glasses compositions have been investigated namely manganese-rich fluorozirconates and strontium fluorohafnates. Numerous fluorophosphate glasses have also been obtained by the incorporation of NaPO 3 and Na 2PO 3F in the unstable MnF 2–BaF 2 and NbO 2F–BaF 2 binary glasses. NMR and electrical conductivity measurements were conducted on these glasses. Rare earth-doped channeled planar waveguides were made from the rare earth doped ZBLA (57%ZrF 4–34%BaF 2–(5 − x)%LaF 3–4%AlF 3– x%REF 3) glass by ionic exchange using optical lithography. The spectroscopic properties of Pr 3+ doped ZBLA planar waveguides were investigated by comparison to bulk samples. For Er 3+/Ce 3+ doped ZBLA channeled waveguide low background losses (0.3 dB/cm) and net gain in excess of 1 dB/cm at 1.5 μm were obtained for incident pump powers higher than 200 mW.

Optical Path Design and Gain Anticipation in Tm<sup>3+</sup> Doped Glass Channel Waveguide for U-Band Amplification

To achieve effective U-band integrated amplification in a cm2 glass substrate, bent waveguide structure (U-bend) based on Tm3+ doped germanate glass substrate has been designed. Using simulated-bend method, the optimal radius for the curved structure is offered to be 2.30 cm with a bending loss coefficient of 0.054 dB/cm. For the U-bend waveguide, the evident signal gain is anticipated in the wavelength range of U-band, and the ideal internal gain is derived to be 5.77 dB at 1675 nm wavelength, which is two times higher than 2.52 dB in the straight one. Simulation results indicate that reasonable optical path design can enhance the optical gain in Tm3+ doped germanate glass channel waveguides considerably, which provides a feasible designing idea in realizing practical applications for U-band amplification devices.

Gain evaluation of compact designing on Er 3+/Yb 3+ codoped germanate glass channel waveguide

Bent waveguide structures (U- and F-bend) based on UV-sensitive Er 3+/Yb 3+ codoped germanate glass substrates have been designed to achieve high-gain C-band amplification. Using simulated-bend method, the optimal radius for curved structure is offered to be 1.90 cm with loss coefficient of 0.0015 dB/cm, as the substrate size is minimally schemed. In the wavelength range of 1528–1559 nm, obvious gain enhancement for the bent structure waveguides is anticipated, while, for the F-bend waveguide, the internal gain at 1533.8 nm wavelength is derived to be 22.55 dB, which is much higher than the value of 14.06 dB in the U-bend waveguide, and over three times higher than that of the straight one, after compensating both the bend loss and the transition loss. The simulation results indicate that the bent structure designing is beneficial in attaining high optical gain in Er 3+/Yb 3+ codoped germanate glass substrates, which assures that long-period grating can be applied to implement practical C-band gain-flattened amplification.

Tm3+掺杂S波段波导放大器的光路设计与增益预期

Tm³⁺掺杂S波段波导放大器的光路设计与增益预期

Proposal for a simple integrated optical ion-exchange waveguide polarizer with a liquid crystal overlay

A simple, compact electro-optic polarizer based on an ion-exchanged glass channel waveguide covered with a nematic liquid crystal (LC) is proposed. A full-vectorial beam propagation method is employed to simulate this device for the first time. For the cases of zero and strong LC surface anchoring, the performance of the proposed polarizer under different applied voltages is analyzed numerically. Analysis indicates that surface anchoring of the liquid crystal is a key issue influencing the performance for the proposed optical polarizer device.