Erbium-doped amplifiers are key elements not only for modern telecom systems but also for integrated narrow linewidth lasers that are used for sensing and THz generation. Ion exchange on glass is a technological platform that allows realizing very efficient erbium-doped waveguide amplifiers with low coupling losses and quite high net gains. However, integrated lasers require a shorter amplifying waveguide that is operated in a strongly saturated regime. For this reason, a co-doping with Er and Yb is used. In this paper, we present the characterizations of Er-Yb co-doped waveguide amplifiers in terms of spectroscopic and guiding properties. Then small signal and satured gains measurements are presented. Finally, all these experimental data are employed to derive and assess a theoretical model of the ion-exchanged waveguide amplifier.
Integrated solid-state lasers have the advantage of offering narrow linewidth, well below the MHz range, making them ideal for various applications, from sensing to telecommunication. High coherence free-running lasers are difficult to characterize, due to the combination of a reduced linewidth with potential frequency drift. Conventional techniques such as optical self-heterodyning solutions require decorrelation lengths of several hundreds of km, and standard RF phase noise measurements are not compatible with slow varying effects due to the presence of frequency drift. In order to analyze the coherence of ion-exchanged co-doped Er-Yb integrated glass lasers during free-running operations, we developed a direct measurement of the optical phase by analyzing heterodyne signals in the time domain. From the analysis of the phase evolution in time, we estimate the linewidth of ion exchange glass lasers, estimated to be 1 kHz, while being able to discriminate optical contributions from slow varying processes generating frequency drift.
Terahertz applications have been extensively studied during the last decade since they allow not only increasing the bandwidth of telecom systems but also the detection of many organic molecules in solid and liquid phase, including hazardous materials such as explosives. In this contribution, we present a device that allows generating frequencies in the Terahertz domain through the heterodyning of signals emitted by two distributed feedback lasers made by ion exchange on a erbium-ytterbium co-doped glass. Thanks to the intrinsic thermal stability of the glass substrate, the slow dynamic of the amplifier medium and since the laser pairs are integrated on a single chip and identically pumped by the same sources, stable frequencies have been generated in the millimeter and sub-Terahertz frequency range, without any thermal or electrical control loop being implemented.
Erbium-doped integrated DFB lasers on glass exhibit a thermal stability and a very narrow linewidth that has been proven useful for many applications ranging from DWDM and Optomicrowave transmissions to airborne LIDAR. If the technologies used for the Erbium-doped active waveguides can differ (alumina, phosphate and silicate glasses have been reported among others), the laser cavity is always obtained thanks to a long Bragg grating implemented on the chip surface. Realizing cm-long submicrometric structure is a challenge that has been successfully overcome, but having such fragile features exposed on the top of a device entails several problems of packaging when reliability is concerned. Until now, this key issue has been addressed by depositing a conformal thin-film on the device surface, which is a complicated task since the deposited layer should be conformal, match the proper refractive index and respect the thermal budget of the process flow. In this paper, we present a different approach for the realization of Er-doped DFB lasers on glass where the grating-based cavity is implemented on a passive wafer that is then flip-chipped and wafer bonded on an Erbiumdoped phosphate glass containing active ion-exchanged waveguides. First results proved that a stable emission at a wavelength of 1.55 μm has been achieved for a fiber-coupled output power of more than 1mW.
Recently, dual mode lasers proved to be interesting sources for radio frequency generation at millimeter wave frequency and beyond, to be used in photonic RoF systems. As the optical modes can eventually be correlated, such sources associate the simplicity of heterodyning technique with the frequency stability. Still, most architectures require active frequency control loop to reach communication requirements to limit frequency drift, and reduce the phase noise of the generated carrier. In this communication, we propose the use of a free running dual mode laser integrated on glass for radio frequency generation. The device is fabricated on an ion-exchanged co-doped Erbium Ytterbium substrate to emit in the C-band. We demonstrate that this device is able to generate an ultra-narrow spectrum radio-frequency carrier, reaching 600Hz spectral linewidth without control loop nor thermal stabilization. As a proof of concept, the device proposed in this work produces a radio frequency at 6.1 GHz which has been evaluated as an electrical carrier in radio transmission experiments. Data rates of several Gbps using complex modulation formats such from BPSK to 64QAM have been successfully tested. The results are compliant with communications standards requirements, validating the use of such a source in Radio over Fibre (RoF) systems. This paper first presents the glass dual-mode laser design, followed by the characterization of the generated carrier to finally present the radio over fiber results.
The search for Earth-like exoplanets, orbiting in the habitable zone of stars other than our Sun and showing biological activity, is one of the most exciting and challenging quests of the present time. Nulling interferometry from space, in the thermal infrared, appears as a promising candidate technique for the task of directly observing extra-solar planets. It has been studied for about 10 years by ESA and NASA in the framework of the Darwin and TPF-I missions respectively [1].
Nevertheless, nulling interferometry in the thermal infrared remains a technological challenge at several levels. Among them, the development of the "modal filter" function is mandatory for the filtering of the wavefronts in adequacy with the objective of rejecting the central star flux to an efficiency of about 105. Modal filtering [2] takes benefit of the capability of single-mode waveguides to transmit a single amplitude function, to eliminate virtually any perturbation of the interfering wavefronts, thus making very high rejection ratios possible.
The modal filter may either be based on single-mode Integrated Optics (IO) and/or Fiber Optics. In this paper, we focus on IO, and more specifically on the progress of the on-going “Integrated Optics” activity of the European Space Agency.
The diversity of integrated photonic sensors such as LIDARs increased in part thanks to integrated laser sources development. Glass integrated lasers fit well sensing demand because of their high durability and great integration potential. We propose here a new kind of saturable absorber (SA) for glass integrated Q-switched lasers, based on a solgel matrix. This is intended to improve durability and output power of existing lasers, whose SA is often based on plastic materials.
While sol-gel is already used for optical limiting devices, its use as a host for SA has not been investigated so far. Due to its interesting properties such as durability, high laser induced damage threshold (LIDT) and coating convenience, it should also be a good candidate to realize a reliable SA matrix.
We mixed a hybrid organic-inorganic sol with toluene and (bis(4_dimethylaminodithiobenzil) nickel – BDN I, a SA dye molecule. Drops of this mix have been coated and annealed to obtain a SA sol-gel thick layer. We modeled BDN I with a four energy-level system and measured its absorption over optical input power at the wavelength of 1064nm in order to extract its physical parameters: absorption cross sections and relaxation time. This SA showed good performances with 30% modulation depth.
This sol-gel has also been spin coated on ion-exchanged glass integrated waveguide. The characteristics of this waveguide SA have been measured and the evanescent light interaction between the waveguide and the saturable absorber layer has been modeled. This study will allow further integrated Q-switched lasers design.
In this work, we propose the realization of two single mode distributed feedback (DFB) lasers emitting at 1.5μm with ultra-narrow linewidths, co-integrated on a co-doped Erbium Ytterbium IOG11 glass substrate. The beating note of these two lasers on a fast photodiode is used to generate mm-wave signals. Each laser is composed of a waveguide fabricated by ion exchange with a Bragg grating etched on the top. In order to set a precise value of the mm-wave frequency, the emission wavelength of both DFB lasers must be accurately fixed. This is achieved by controlling the laser’s waveguide design. The beating produced between these lasers generates mm-wave signals from GHz to THz. The co-integration helps to enhance the beating quality by reducing fluctuations between the two lasers. Lasers are first studied independently: their optical power, linewidth and relative intensity noise are characterized. Finally, the beating signal quality is estimated through the characterization of the produced electrical spectrum.
The development of pulsed lasers allows increasing the power density into integrated waveguides to a level compatible with the generation of nonlinear phenomena, opening the route to the realization of integrated supercontinuum sources. In this paper, we investigate the spectral broadening of a laser pulse through Raman scattering processes in normal dispersion regime with nanosecond pumping. The obtained experimental results are compared to an experimental model based on a single fiber with the same confinement and perspectives in terms of integrated broadband sources are presented.
A passively Q-switched distributed-Bragg-reflector laser made in glass integrated optics technology, and operating around 1030 nm, is designed, realized and investigated. The laser is formed by an ion-exchanged single mode waveguide realized in an Ytterbium doped phosphate glass. The Q-switching behavior is obtained by hybridizing a saturable absorber film on the waveguides. This allows the realization of a short and simple laser cavity having both pulsed and a narrow linewidth emission. Its experimental characterization leads to the observation of a stable repetition rate of 12.5 kHz and a stable pulse duration of 9.2 ns FWHM.
Distributed Feed Back (DFB) lasers working in the third telecom window are essential for optical communications, eyesafe
sensors and lab-on-chip devices. Glass integrated optics technology allows realizing such devices by using rareearth
doped substrates. Despite their good output power and spectral characteristic, DFB lasers still present some
reliability issues concerning the Bragg grating protection. Moreover Erbium doped glasses are not compatible with the
realization of passive optical functions. In order to solve the DFB lasers reliability issues and to ensure a monolithic
integration between active and passive functions, we propose an hybrid-device architecture based on ion-exchange
technology and wafer bonding. The Ag+/Na+ ion-exchange in the silicate glass wafer is used to realize the passive
functions and the lateral confinement of the electromagnetic field. Through a second ion exchange step, a slab
waveguide is made on the Erbium-Ytterbium doped glass wafer. The Bragg grating is processed on the passive substrate
and the two glasses are bonded. The potential of this structure has been demonstrated through the realization of a DFB
hybrid laser with a fully encapsulated Bragg grating.
Mode-lock lasers have been studied a lot in the past years for producing pulses as short as possible. These
devices have mostly been realized in bulk optics and they are consequently cumbersome and sensitive to
vibrations. There are only a few studies on integrated optics mode-lock lasers, though this technology is very
promising because of its stability, compactness and the possibility to integrate several functions on a single chip.
In this paper, we present an ion-exchange passively mode-locked laser in dissipative soliton operation. One of
the key characteristics of this structure is its mechanical stability. Indeed, no bulk optics is needed because the
saturable absorber is hybridized on the top of the waveguide in order to interact with the evanescent part of the
guided mode. Indeed, the device that has been obtained is composed of an ion-exchanged single mode
waveguide realized in a Neodymium doped phosphate glass. The laser feedback is produced by a Fabry-Perot
cavity realized with two multilayers dielectric mirrors stuck on the waveguides facets. We implemented a bis(4-
dimethylaminodithiobenzil)nickel (BDN) dye included in a cellulose acetate thick film, which presents a
saturable absorber behaviour around 1.06 μm. With this structure, pulses with repetition rates of 3.3 GHz and a
single mode output have been measured. Moreover, the use of an autocorrelation set-up allowed us measuring
picosecond pulse durations.
In this paper, we present the development of a laser source for a LIDAR application. This sensor is proposed as a standby instrument to provide a way to measure some aircraft air data such as the air speed. Although such systems already exist, none of them are based on an optical measurement. Thus, the use of a LIDAR would provide a backup channel with different failure modes than existing systems. Our LIDAR system allows determining the air speed through Doppler measurement at a wavelength of 1.55 µm on aerosol particles present around the aircraft. The core of this device is a glass integrated optics continuous DFB laser. Its performances in term of single-frequency, stability, noise and linewidth are assessed in order to ensure the correct operation of the LIDAR system.
In the mid 80's, the doping of optical fiber's core with rare earth atoms has been a major breakthrough in the field of
optical telecommunications since it allowed the realization of in-line optical amplifiers. However, erbium-doped fiber
amplifiers are a few meters long and a huge effort has been made in order to realize compact and efficient active devices
based on rare-earth-doped waveguides. For this purpose the use of phosphate glasses instead of silicate ones has been
investigated because they allow a better solubility of the inserted rare earths. In this paper we present the realization of a
hybrid Neodymium-doped passively Q-switched waveguide laser made by ion exchange on a Schott IOG-1 phosphate
laser glass combined with the deposition of a BDN saturable absorber diluted in a cellulose acetate polymer cladding. In
a first step, we present the CW operation of the laser with an undoped cladding. We show that for a 3.5-μm wide, 1.4-cm
long waveguide realized by a silver-sodium ion exchange, a 6 mW output has been achieved by creating a Fabry-Perot
cavity with dielectric multilayers mirrors sticked to the chip facets. Then, the characterizations performed on the BDN
doped layers are presented. It is shown that a proper selection of the hybrid guiding structure and saturable absorber
concentration entail an excess absorption ranging from 1 to 10 dB/cm at zero flux. Finally, results on Q-switched
behavior are presented. Optical pulse duration of 2-ns (FWHM) was obtained with repetition rates ranging from 5 to
around 50 kHz for a 22 W pulse peak power.
High coherence glass DFB lasers emitting in the 1550 nm window are useful for many applications, including eyesafe sensors and DWDM telecommunication systems. One of the key characteristic of lasers designed for sensor or telecommunications applications is their monomode behaviour. A standard DFB laser indeed emits two wavelengths located at both sides of the grating stop band. A quarter-wave phase shift is thus required in the center of the grating in order to make a single mode laser. In this paper, we present a new kind of phase shift, that was initially developped for semiconductor lasers but never applied to glass or fiber optics lasers. The main advantage of this technique is that the phase shift is realized during the waveguide photolithography process so that there is no need of any additionnal step. Moreover, its design ensures that the value of the phase shift can be very accurately set, which enables to realize a grating cavity with a unique lasing wavelength. Both theoretical and experimental results on these new phase shifted lasers are presented and a SMSR of more than 50dB is presented.
This paper presents the realization and characterization of ultra narrow linewidth DFB lasers realized by ion-exchange on Er/Yb codoped glass substrates. Output power characteristics such as power efficiency and relative intensity noise are presented. Spectral behavior such as linewidth, wavelength stability versus temperature and emission wavelength calibration are also investigated. Indeed, a fully connectorized DFB with 4.5 mW output power and a 3 kHz narrow linewidth is presented.
This paper presents the realization and characerization of a matrix of DFB lasers realized by ion-exchange on Er/Yb codoped glass substrate. Output power characteristics such as power efficiency and Relative Intensity Noise are presented, wavelength characteristics including linewidth, wavelength stability versus temperature and emission wavelength calibration are also investigated. Concerning output power, a 4.5 mW fiber coupled emission was achieved and a low RIN falling below -150bB/Hz after 4 MHz was measured. The matrix contains 15 lasers emitting at 100 or 25 GHz spaced frequencies with a very narrow linewidth measured to be 3 kHz. Finally, the temperature dependency of the comb of wavelength is measured to be 1.3 GHz/°C.
Nowadays, optical telecommunication systems require an increasing bit-rate. For this reason Dense Wavelength Division Multiplexing (DWDM) systems are currently under development. They need optical sources with a narrow and stable emission spectrum in the C band which should also integrate several emission wavelengths. Glass waveguide lasers enable both the sharp linewidth of optical fiber lasers and the integration possibilities of semiconductor lasers. In this paper, the realization of ion-exchanged waveguide DFB lasers on glass substrates is presented. Phosphate Er-Yb-codoped glass integrated lasers are first investigated for different doping concentrations. The characteristics of these lasers are then compared : each one have low threshold and exhibit single mode output power of several milliwatt for 100 mW launched pump power. The effect of a passivation layer is then studied. Its modelling and experiment shows that the emitted power can be increased by reducing pump scattering losses. Thanks to the use of silver ion exchange technology, a high index increase is obtained which induces an important variation of the waveguide's effective index with its width. Thus, the emission of 15 channels roughly placed on the 100 GHz ITU grid is demonstrated.
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