FOTONICA - Grup de Recerca de Fotònica
http://hdl.handle.net/2117/3270
2017-03-25T10:13:02ZUltrasensitive interferometric on-chip microscopy of transparent objects
http://hdl.handle.net/2117/102826
Ultrasensitive interferometric on-chip microscopy of transparent objects
Terborg, Roland A.; Pello, Josselin; Mannelli, Ilaria; Pérez Torres, Juan; Pruneri, Valerio
Light microscopes can detect objects through several physical processes, such as scattering, absorption, and reflection. In transparent objects, these mechanisms are often too weak, and interference effects are more suitable to observe the tiny refractive index variations that produce phase shifts. We propose an on-chip microscope design that exploits birefringence in an unconventional geometry. It makes use of two sheared and quasi-overlapped illuminating beams experiencing relative phase shifts when going through the object, and a complementary metal-oxide-semiconductor image sensor array to record the resulting interference pattern. Unlike conventional microscopes, the beams are unfocused, leading to a very large field of view (20 mm(2)) and detection volume (more than 0.5 cm(3)), at the expense of lateral resolution. The high axial sensitivity (<1 nm) achieved using a novel phase-shifting interferometric operation makes the proposed device ideal for examining transparent substrates and reading microarrays of biomarkers. This is demonstrated by detecting nanometer-thick surface modulations on glass and single and double protein layers.
2017-03-23T12:57:15ZTerborg, Roland A.Pello, JosselinMannelli, IlariaPérez Torres, JuanPruneri, ValerioLight microscopes can detect objects through several physical processes, such as scattering, absorption, and reflection. In transparent objects, these mechanisms are often too weak, and interference effects are more suitable to observe the tiny refractive index variations that produce phase shifts. We propose an on-chip microscope design that exploits birefringence in an unconventional geometry. It makes use of two sheared and quasi-overlapped illuminating beams experiencing relative phase shifts when going through the object, and a complementary metal-oxide-semiconductor image sensor array to record the resulting interference pattern. Unlike conventional microscopes, the beams are unfocused, leading to a very large field of view (20 mm(2)) and detection volume (more than 0.5 cm(3)), at the expense of lateral resolution. The high axial sensitivity (<1 nm) achieved using a novel phase-shifting interferometric operation makes the proposed device ideal for examining transparent substrates and reading microarrays of biomarkers. This is demonstrated by detecting nanometer-thick surface modulations on glass and single and double protein layers.Trapping of light beams and formation of spatial solitary waves in quadratic nonlinear media
http://hdl.handle.net/2117/102812
Trapping of light beams and formation of spatial solitary waves in quadratic nonlinear media
Torner Sabata, Lluís; Torruellas, W; Stegeman, G; Menyuk, C; Wright, E
Summary form only given. In this paper we report the outcome of our comprehensive investigations to study the dynamics of the beam trapping in both bulk crystals and optical planar waveguides made of quadratic nonlinear media in second-harmonic generation configurations. We address and discuss the suitable experimental conditions required to form spatial solitary waves in critical phase-matching and quasi-phase-matching settings.
2017-03-22T17:03:34ZTorner Sabata, LluísTorruellas, WStegeman, GMenyuk, CWright, ESummary form only given. In this paper we report the outcome of our comprehensive investigations to study the dynamics of the beam trapping in both bulk crystals and optical planar waveguides made of quadratic nonlinear media in second-harmonic generation configurations. We address and discuss the suitable experimental conditions required to form spatial solitary waves in critical phase-matching and quasi-phase-matching settings.Frequency conversion of structured light
http://hdl.handle.net/2117/102277
Frequency conversion of structured light
Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Pérez Torres, Juan
Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803¿nm) to the visible (527¿nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging.
2017-03-10T10:51:14ZSteinlechner, FabianHermosa, NathanielPruneri, ValerioPérez Torres, JuanCoherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803¿nm) to the visible (527¿nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging.Weak value amplification: a view from quantum estimation theory that highlights what it is and what isn’t
http://hdl.handle.net/2117/102273
Weak value amplification: a view from quantum estimation theory that highlights what it is and what isn’t
Pérez Torres, Juan; Salazar Serrano, Luis Jose
Weak value amplification (WVA) is a concept that has been extensively used in a myriad of applications with the aim of rendering measurable tiny changes of a variable of interest. In spite of this, there is still an on-going debate about its true nature and whether is really needed for achieving high sensitivity. Here we aim at helping to clarify the puzzle, using a specific example and some basic concepts from quantum estimation theory, highlighting what the use of the WVA concept can offer and what it can not. While WVA cannot be used to go beyond some fundamental sensitivity limits that arise from considering the full nature of the quantum states, WVA can notwithstanding enhance the sensitivity of real and specific detection schemes that are limited by many other things apart from the quantum nature of the states involved, i.e. technical noise. Importantly, it can do that in a straightforward and easily accessible manner.
2017-03-10T10:27:25ZPérez Torres, JuanSalazar Serrano, Luis JoseWeak value amplification (WVA) is a concept that has been extensively used in a myriad of applications with the aim of rendering measurable tiny changes of a variable of interest. In spite of this, there is still an on-going debate about its true nature and whether is really needed for achieving high sensitivity. Here we aim at helping to clarify the puzzle, using a specific example and some basic concepts from quantum estimation theory, highlighting what the use of the WVA concept can offer and what it can not. While WVA cannot be used to go beyond some fundamental sensitivity limits that arise from considering the full nature of the quantum states, WVA can notwithstanding enhance the sensitivity of real and specific detection schemes that are limited by many other things apart from the quantum nature of the states involved, i.e. technical noise. Importantly, it can do that in a straightforward and easily accessible manner.Rotating vortex clusters in media with inhomogeneous defocusing nonlinearity
http://hdl.handle.net/2117/102043
Rotating vortex clusters in media with inhomogeneous defocusing nonlinearity
Kartashov, Yaroslav V.; Malomed, Boris A.; Vysloukh, Victor A.; Belic, Milivoj R.; Torner Sabata, Lluís
We show that media with inhomogeneous defocusing cubic nonlinearity growing toward the periphery can support a variety of stable vortex clusters nested in a common localized envelope. Nonrotating symmetric clusters are built from an even number of vortices with opposite topological charges, located at equal distances from the origin. Rotation makes the clusters strongly asymmetric, as the centrifugal force shifts some vortices to the periphery, while others approach the origin, depending on the topological charge. We obtain such asymmetric clusters as stationary states in the rotating coordinate frame, identify their existence domains, and show that the rotation may stabilize some of them.
2017-03-07T11:55:42ZKartashov, Yaroslav V.Malomed, Boris A.Vysloukh, Victor A.Belic, Milivoj R.Torner Sabata, LluísWe show that media with inhomogeneous defocusing cubic nonlinearity growing toward the periphery can support a variety of stable vortex clusters nested in a common localized envelope. Nonrotating symmetric clusters are built from an even number of vortices with opposite topological charges, located at equal distances from the origin. Rotation makes the clusters strongly asymmetric, as the centrifugal force shifts some vortices to the periphery, while others approach the origin, depending on the topological charge. We obtain such asymmetric clusters as stationary states in the rotating coordinate frame, identify their existence domains, and show that the rotation may stabilize some of them.A 3D printed toolbox for opto-mechanical components
http://hdl.handle.net/2117/100862
A 3D printed toolbox for opto-mechanical components
Salazar Serrano, Luis Jose; Pérez Torres, Juan; Valencia, Alejandra
In this article we present the development of a set of opto-mechanical components (a kinematic mount, a translation stage and an integrating sphere) that can be easily built using a 3D printer based on Fused Filament Fabrication (FFF) and parts that can be found in any hardware store. Here we provide a brief description of the 3D models used and some details on the fabrication process. Moreover, with the help of three simple experimental setups, we evaluate the performance of the opto-mechanical components developed by doing a quantitative comparison with its commercial counterparts. Our results indicate that the components fabricated are highly customizable, low-cost, require a short time to be fabricated and surprisingly, offer a performance that compares favorably with respect to low-end commercial alternatives.
2017-02-10T14:28:16ZSalazar Serrano, Luis JosePérez Torres, JuanValencia, AlejandraIn this article we present the development of a set of opto-mechanical components (a kinematic mount, a translation stage and an integrating sphere) that can be easily built using a 3D printer based on Fused Filament Fabrication (FFF) and parts that can be found in any hardware store. Here we provide a brief description of the 3D models used and some details on the fabrication process. Moreover, with the help of three simple experimental setups, we evaluate the performance of the opto-mechanical components developed by doing a quantitative comparison with its commercial counterparts. Our results indicate that the components fabricated are highly customizable, low-cost, require a short time to be fabricated and surprisingly, offer a performance that compares favorably with respect to low-end commercial alternatives.A measure of flow vorticity with twisted beams of light
http://hdl.handle.net/2117/100606
A measure of flow vorticity with twisted beams of light
Belmonte Molina, Aniceto; Rosales Guzmán, Carmelo; Pérez Torres, Juan
The measurement of vorticity, a parameter providing local measurements of
rotation at every point in a flow, would greatly assist research fields as diverse as biology microfluidics, complex motions in the oceanic and atmospheric boundary layers, and wake turbulence on fluid aerodynamics. However, the precise measurement of flow vorticity is difficult. Here, we devise an experiment in which the local vorticity of a flow can be estimated by probing the fluid with Laguerre-Gauss beams, optical beams that show an azimuthal phase variation that is the origin of its characteristic non-zero orbital angular momentum. The key point is to make use of the transversal Doppler effect of the returned signal that depends only on the azimuthal component of the flow velocity along the ringshaped
observation beam. We found from a detailed analysis of the experimental method
that probing the fluid with LG beams is an effective and simple sensing technique capable to produce accurate estimates of flow vorticity.
2017-02-07T09:01:35ZBelmonte Molina, AnicetoRosales Guzmán, CarmeloPérez Torres, JuanThe measurement of vorticity, a parameter providing local measurements of
rotation at every point in a flow, would greatly assist research fields as diverse as biology microfluidics, complex motions in the oceanic and atmospheric boundary layers, and wake turbulence on fluid aerodynamics. However, the precise measurement of flow vorticity is difficult. Here, we devise an experiment in which the local vorticity of a flow can be estimated by probing the fluid with Laguerre-Gauss beams, optical beams that show an azimuthal phase variation that is the origin of its characteristic non-zero orbital angular momentum. The key point is to make use of the transversal Doppler effect of the returned signal that depends only on the azimuthal component of the flow velocity along the ringshaped
observation beam. We found from a detailed analysis of the experimental method
that probing the fluid with LG beams is an effective and simple sensing technique capable to produce accurate estimates of flow vorticity.Vector mixed-gap surface solitons
http://hdl.handle.net/2117/100241
Vector mixed-gap surface solitons
Kartashov, Yaroslav V.; Ye, F; Torner Sabata, Lluís
We elucidate the properties of mixed-gap vector surface solitons supported by the interface between a uniform medium and an optical lattice imprinted in a Kerr-type nonlinear media. The components of such mixed-gap solitons emerge from different gaps of lattice spectrum and their mutual trapping results in the formation of stable vector states. The unstable soliton component is stabilized by the cross-coupling with the stable component. We show that vector mixed-gap surface solitons exhibit a new combination of properties of vectorial surface waves and gap solitons.
2017-01-27T17:28:04ZKartashov, Yaroslav V.Ye, FTorner Sabata, LluísWe elucidate the properties of mixed-gap vector surface solitons supported by the interface between a uniform medium and an optical lattice imprinted in a Kerr-type nonlinear media. The components of such mixed-gap solitons emerge from different gaps of lattice spectrum and their mutual trapping results in the formation of stable vector states. The unstable soliton component is stabilized by the cross-coupling with the stable component. We show that vector mixed-gap surface solitons exhibit a new combination of properties of vectorial surface waves and gap solitons.Sensitivity study of the microwave spiralimetric imaging
http://hdl.handle.net/2117/100239
Sensitivity study of the microwave spiralimetric imaging
Jofre Roca, Lluís; Blanch Boris, Sebastián; Cardama Aznar, Ángel; Rius Casals, Juan Manuel; Torner Sabata, Lluís
The use of the spiral modes-electromagnetically related to the orbital momentum of the photons- at microwave frequencies for imaging purposes is studied and some preliminary numerical and experimental results for basic canonical geometries are presented and discussed
2017-01-27T17:19:19ZJofre Roca, LluísBlanch Boris, SebastiánCardama Aznar, ÁngelRius Casals, Juan ManuelTorner Sabata, LluísThe use of the spiral modes-electromagnetically related to the orbital momentum of the photons- at microwave frequencies for imaging purposes is studied and some preliminary numerical and experimental results for basic canonical geometries are presented and discussedObservation of Dyakonov surface waves
http://hdl.handle.net/2117/100238
Observation of Dyakonov surface waves
Takayama, Osamu; Crasovan, I; Artigas García, David; Torner Sabata, Lluís
Summary form only given. A special type of surface wave was predicted by M. I. Dyakonov in 1988. Such waves exist under special conditions at the interface of transparent anisotropic materials, and hens they are lossless. This surface waves require at least one of the two media to be an anisotropic medium, either biaxial or positive uniaxial, and various configurations have been investigated. In the case of the interface of a biaxial anisotropic medium with refractive indices nx, ny and nz, and an isotropic medium with refractive indices nc, surface waves form only when the refractive indices fulfill the condition n1 > nc > n2 > n3, where n1 = max (nx ; ny ; nz), n3 = min (nx ; ny ; nz) and, n2 is in between n1 and n3,. For a positive uniaxial medium, the condition becomes nc > nc > no, where no and nc are the ordinary and extraordinary refractive indices, respectively. When such a condition is fulfilled, hybrid surface waves containing both ordinary and extraordinary field components propagate within a narrow angular band, Deltathetas, with respect to the crystal optical axis. The allowed propagation angles are referred to as the angular existence domain. The condition is difficult to meet with standard available crystals, making difficult the observation of Dyakonov waves . Here we report on their first observation. Our experiment was conducted in a structure based on a potassium titanyl phosphate (KTP) crystal at lambda = 632.8 nm and index matching liquids with refractive indices that satisfy the given condition. We used a modified Otto-Kretchmann configuration which is composed of a prism, an isotropic liquid layer, and KTP substrate to excite the surface wave at the liquid-KTP interface. Surface wave excitation was detected by imaging the reflected beam. We conducted experiments with five different index matching liquids, and measured the cutoff angle, thetasmax, where the reflected peak associated with the Dyakonov surface wave disappears. The paper illustrates a potential application of Dyakonov surface waves as high sensitive refractive index sensors. The influence of the different structural parameters, such as the thickness of the isotropic layer as on the excitation is discussed.
2017-01-27T17:18:13ZTakayama, OsamuCrasovan, IArtigas García, DavidTorner Sabata, LluísSummary form only given. A special type of surface wave was predicted by M. I. Dyakonov in 1988. Such waves exist under special conditions at the interface of transparent anisotropic materials, and hens they are lossless. This surface waves require at least one of the two media to be an anisotropic medium, either biaxial or positive uniaxial, and various configurations have been investigated. In the case of the interface of a biaxial anisotropic medium with refractive indices nx, ny and nz, and an isotropic medium with refractive indices nc, surface waves form only when the refractive indices fulfill the condition n1 > nc > n2 > n3, where n1 = max (nx ; ny ; nz), n3 = min (nx ; ny ; nz) and, n2 is in between n1 and n3,. For a positive uniaxial medium, the condition becomes nc > nc > no, where no and nc are the ordinary and extraordinary refractive indices, respectively. When such a condition is fulfilled, hybrid surface waves containing both ordinary and extraordinary field components propagate within a narrow angular band, Deltathetas, with respect to the crystal optical axis. The allowed propagation angles are referred to as the angular existence domain. The condition is difficult to meet with standard available crystals, making difficult the observation of Dyakonov waves . Here we report on their first observation. Our experiment was conducted in a structure based on a potassium titanyl phosphate (KTP) crystal at lambda = 632.8 nm and index matching liquids with refractive indices that satisfy the given condition. We used a modified Otto-Kretchmann configuration which is composed of a prism, an isotropic liquid layer, and KTP substrate to excite the surface wave at the liquid-KTP interface. Surface wave excitation was detected by imaging the reflected beam. We conducted experiments with five different index matching liquids, and measured the cutoff angle, thetasmax, where the reflected peak associated with the Dyakonov surface wave disappears. The paper illustrates a potential application of Dyakonov surface waves as high sensitive refractive index sensors. The influence of the different structural parameters, such as the thickness of the isotropic layer as on the excitation is discussed.