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Multimode near-stoichiometric (NS) Ti:LiNbO3 planar waveguide was fabricated by Ti-diffusion followed by post-Li-rich vapor transport equilibration. The crystalline phase, composition and guided modes in the planar waveguide were characterized. The refractive index profile in the waveguide is constructed from the measured mode indices using the inverse Wentzel–Krames–Brillouin method and correlated with the Ti profile obtained from secondary ion mass spectroscopy analysis. The results show that the LiNbO3 phase dominates in the waveguide layer and the waveguide has an NS composition. The index increase has a linear relation to Ti-concentration for both cases of ordinary and extraordinary rays, and the relationship is considerably different from those of some congruent or NS bulk materials or waveguides. A comparison of various congruent and NS bulk materials or waveguides allows to conclude that the relationship changes from congruent to NS composition, from one fabrication method to another and from bulk material to waveguide configuration. [ABSTRACT FROM PUBLISHER]

We report Sc3+-doped Ti:LiNbO3 (Ti:Sc:LN) strip waveguide fabricated by Ti-diffusion following homogeneous Sc3+-diffusion-doping in a Z-cut congruent substrate. We show that Sc3+-doping has little contribution to the substrate index and the Li2O out-diffusion was effectively suppressed. The refractive index increases in the waveguide layer are mainly contributed from the Ti4+ dopants. The waveguide well supports both transverse electric (TE) and magnetic (TM) modes, is single-mode at 1.5-μm wavelength, and has a loss of 1.4 dB/cm for the TE mode and 1.8 dB/cm for the TM mode. A secondary ion mass spectrometry study shows that the Sc3+-profile covers 80% ordinary refractive index profile and almost 100% extraordinary refractive index profile, and the 1/e Sc3+ concentration is above the threshold of photorefractive effect. Further, two-beam hologram recording experimental results verify the optical-damage-resistant feature of the waveguide. Highlights are given for fabrication of an optical-damage-resistant Ti:Sc:LN waveguide. [ABSTRACT FROM PUBLISHER]

Multimode Ti4+-diffused LiNbO3 planar waveguide doped with Sc3+ ions was fabricated by codiffusion of stacked Sc2O3 and Ti-metal thin film coated onto Z-cut congruent LiNbO3 substrate at 1060 °C in wet O2. The Ti4+-concentration was profiled by secondary ion mass spectrometry. The refractive index profile is constructed from measured mode index, and correlated with the Ti4+ profile. Other two related issues including the contribution of Sc3+-doping to substrate refractive index and Li2O out-diffusion were also studied. The results show that the Sc3+-doping has little contribution to the substrate index and the Li2O out-diffusion was effectively suppressed. The index change and Ti 4+-concentration follow an exponential relationship with a power index 0.54/0.79 for the ordinary/extraordinary ray. The relationship is similar to that of conventional Ti:LiNbO3 waveguide because of little contribution of Sc3+-doping to the substrate index and effective suppression for Li2O out-diffusion. Some considerations for fabricating an optical-damage-resistant Ti:Sc:LiNbO3 waveguide are given. [ABSTRACT FROM PUBLISHER]

We report a Ti:Er:LiNbO3 strip waveguide with high diffusion-doped surface Er3+ concentration. The waveguide was fabricated with a technological process in sequence of preparation of noncongruent, Li-deficient LiNbO3 substrate by performing Li-poor vapor transport equilibration treatment on a congruent Z-cut LiNbO3 plate, diffusion of 40-nm-thick Er metal film, and fabrication of 8-μm-wide Ti-diffused strip waveguide. The waveguide retains the LiNbO3 phase and shows the waveguiding characteristics similar to the conventional Ti:LiNbO3 waveguide. Secondary ion mass spectrometry study shows that the Er3+ diffusion reservoir was exhausted and the profile is Gaussian with a surface concentration two times larger than that of the conventional Ti:Er:LiNbO3 waveguide. The waveguide shows stable 1547-nm small-signal enhancement under the 1480-nm pumping without serious optical damage observed, and a 5-dB signal enhancement is obtained for the available coupled pump power of only 90 mW. A saturated net gain as much as 5 dB/cm is predicted theoretically. [ABSTRACT FROM PUBLISHER]

We report optical-damage-resistant Ti:Er:LiNbO3 strip waveguide with high diffusion-doped surface Er^3+ concentration. The waveguide was fabricated starting from a commercial X-cut congruent LiNbO 3 plate with a two-step technological process in sequence of simultaneous work of Er^3+ diffusion doping and Li-poor vapor transport equilibration treatment, and fabrication of 6-μm-wide Ti-diffused strip waveguide (Z-propagation). The waveguide retains still the LiNbO3 phase and has the waveguiding characteristics similar to the conventional Ti:LiNbO3 waveguide except with a larger loss due to the imperfection of waveguide. Secondary ion mass spectrometry study shows that the Er^3+ diffusion reservoir was exhausted and the profile is the desired Gaussian-type with a surface concentration 1.0 mol%, which is about two times larger than the value of conventional Ti:Er:LiNbO3 amplifier. Further optical characterization shows that the waveguide shows stable 1547 nm small-signal gain under the 980 nm pumping without serious photorefractive effect observed. An unsaturated gain 1.7 dB/cm is obtained for the available coupled pump power of 160 mW. With increased pump power, optimized Er ^3+ diffusion condition and degraded loss figure, a higher gain is expected. [ABSTRACT FROM PUBLISHER]

We have measured the polarized visible and near-infrared, and unpolarized mid-infrared (2.7 \mum) emission spectra of photorefractive-damage-resistant locally Er-Mg-doped near-stoichiometric (NS) Ti:Mg:Er:LiNbO3 strip waveguide, fabricated on an X-cut initially congruent LiNbO3 substrate in sequence by local Er doping in air, Mg-Ti pre-diffusion in wet O2 and post Li-rich vapor transport equilibration treatment. From the measured emission spectra, the emission and absorption cross section spectra were calculated based upon McCumber theory. The spectroscopic features are discussed in comparison with the spectra recorded from the area outside the waveguide, and with the previously reported results of bulk-doped NS Er:Mg:LiNbO3 crystals and congruent Er:LiNbO3 bulk material or Ti:Er:LiNbO3 waveguide structure. The results show that the spectra of the NS waveguide are traditional and reveal small differences from those spectra outside the waveguide in spectral shape, polarization dependence, as well as cross section values. In contrast, the cross section values of the NS waveguide show considerable differences from those of bulk-doped NS material and congruent bulk material or waveguide structure. The 552, 673, 996, and 1531 nm emission lifetimes of the Er^3+ ions outside the waveguide were also measured, and found to be comparable to the results of the bulk-doped NS crystal and the congruent bulk material or waveguide structure. [ABSTRACT FROM PUBLISHER]

We report that the polarization property of \Er^3+ transition in \LiNbO3 waveguide or bulk material is closely related to the incident direction of excitation beam relative to the optical axis of the crystal. It is found that the 1.5-\mu\m transition is highly \sigma- (\pi-) polarized as the excitation direction is perpendicular (parallel) to the optical axis, and the 0.67-\mu\m transition reveals a reversed effect. Incident perpendicularly (parallel), the transition is highly \pi- (\sigma-) polarized. The effect is found to be independent of the polarization state and wavelength of the excitation light. It is attributed to the selective Er site excitation. [ABSTRACT FROM PUBLISHER]

A special structure of a strip Ti : \LiNbO3 waveguide embedded in a planar Ti : \LiNbO3 waveguide is proposed to fabricate a long-period waveguide grating (LPWG). Its applicability is demonstrated by fabricating a long-period grating on the waveguide surface using usual photoresist. We show that an LPWG device based on such a special structure is thermally stable. [ABSTRACT FROM PUBLISHER]

Alkaline aluminum phosphate glasses (NMAP) with excellent chemical durability for thermal ion-exchanged optical waveguide have been designed and investigated. The transition temperature T g (470 °C) is higher than the ion-exchange temperature (390 °C), which is favorable to sustain the stability of the glass structure for planar waveguide fabrication. The effective diffusion coefficient D e of K + –Na + ion exchange in NMAP glasses is 0.110 μm 2 /min, indicating that ion exchange can be achieved efficiently in the optical glasses. Single-mode channel waveguide has been fabricated on Er 3+ /Yb 3+ doped NMAP glass substrate by standard micro-fabrication and K + –Na + ion exchange. The mode field diameter is 9.6 μm in the horizontal direction and 6.0 μm in the vertical direction, respectively, indicating an excellent overlap with a standard single-mode fiber. Judd–Ofelt intensity parameter Ω 2 is 5.47 × 10 −20 cm 2 , implying a strong asymmetrical and covalent environment around Er 3+ in the optical glasses. The full width at half maximum and maximum stimulated emission cross section of the 4 I 13/2 → 4 I 15/2 are 30 nm and 6.80 × 10 −21 cm 2 , respectively, demonstrating that the phosphate glasses are potential glass candidates in developing compact optoelectronic devices. Pr 3+ , Tm 3+ and Ho 3+ doped NMAP glasses are promising candidates to fabricate waveguide amplifiers and lasers operating at special telecommunication windows. [ABSTRACT FROM AUTHOR]

Abstract: Trivalent samarium ion (Sm3+) doped SU8 polymer materials were synthesized and characterized. Intense red emission at 645nm was observed under UV laser light excitation. Spectroscopic investigations show that the doped materials are suitable for realizing planar optical waveguide amplifiers. About 100μm wide multimode Sm3+-doped SU8 channel waveguides were fabricated using a simple UV exposure process. At 250mW, 351nm UV pump power, a signal enhancement of ∼7.4dB at 645nm was obtained for a 15mm long channel waveguide. [Copyright &y& Elsevier]

Low-loss gallium(Ga 3+ )-diffused erbium(Er 3+ )-doped LiTaO 3 (Ga:Er:LiTaO 3 ) channel waveguide was fabricated using erbium metal film diffusion followed by photolithographically patterned gallium oxide(Ga 2 O 3 ) strip diffusion. Secondary ion mass spectrometry analysis shows that Er 3+ concentration follows a Gaussian profile, Ga 3+ concentration follows a sum of two error functions at the waveguide surface and a Gaussian profile in the depth direction. Optical studies show that the waveguide supports single-mode propagation at 1.5 μm wavelength with a coupling loss <1 dB and a waveguide loss 0.2(0.3) dB/cm for the TE(TM) mode, and with a small polarization dependence in mode field distribution. Stable optical gain of ∼1.0 dB/cm was measured at 1547 nm wavelength with 220 mW pump power of 980 nm wavelength, indicating good photorefractive damage resistance of the waveguide. [ABSTRACT FROM AUTHOR]

Abstract: Secondary ion mass spectrometry (SIMS) was used to study the diffusion properties of Mg2+ and Ti4+ ions in a peculiar optical-damage-resistant near-stoichiometric (NS) Ti:Mg:LiNbO3 waveguide structure that a number of strip waveguides are embedded in a planar waveguide. The structure was fabricated on an initially congruent, undoped Z-cut substrate with a technological process in sequence of planar waveguide, strip waveguide, MgO diffusion and post Li-rich vapor transport equilibration (VTE) treatment. The results show that the Mg2+-profiles in both strip and planar waveguide layers are desirably homogeneous with a concentration 1.7±0.3mol% above the optical damage concentration threshold. The Ti4+-profile in the strip waveguide follows a sum of two error functions along the lateral direction with a width 13±1.0μm and a sum of two Gaussian functions in the depth direction with a 1/e depth of ∼11μm all. The Ti4+ ions in the planar waveguide obey a Gaussian profile. From the measured profiles, characteristic diffusion parameters such as mean Mg2+ and Ti4+ diffusivities and surface Ti4+-concentration are evaluated. The diffusivity is discussed in comparison with the previously reported results on single Mg2+, Ti4+ diffusion and Mg2+/Ti4+ co-diffusion in pure (or bulk MgO-doped), congruent (or NS) LiNbO3 crystal. Finally, the keys to the succeeding in fabrication are highlighted. [Copyright &y& Elsevier]