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The article presents a clinical case of a 23-year-old patient with an extremely severe congenital form of chronic intestinal pseudoobstruction coupled with a neuromyopathy,colon malrotation, malabsorption, bacterial overgrowth syndrome, cholelithiasis and gastrostasis, which excluded bowel transplantation. Long-term treatment in the intensive care unit with combined, mainly parenteral nutrition for 6 months, using antibiotics, prokinetics, intestinal decompression allowed to achieve partial stabilization of the patients condition and transfer to home treatment with the continuation of adequate complex therapy.Представлено клиническое наблюдение больной 23 лет с крайне тяжелой врожденной формой хронической интестинальной псевдообструкции с нейромиопатией. мальротацией толстой кишки, мальабсорбцией, синдромом избыточного бактериального роста, холелитиазом, гастростазом, исключавшим выполнение трансплантации кишечника. Длительное лечение в отделении интенсивной терапии с комбинированным, преимущественно парентеральным питанием в течение 6 мес, применением антибиотиков, прокинетиков, кишечной декомпрессии позволило добиться частичной стабилизации состояния и перевода пациентки на домашнее лечение с продолжением адекватной комплексной терапии.

National audience

The lensless endoscope represents the ultimate limit in miniaturization of imaging tools: an image can be transmitted through a (multi-mode or multi-core) fiber by numerical or physical inversion of the fiber's pre- measured transmission matrix. However, the transmission matrix changes completely with only minute conformational changes of the fiber, which has so far limited lensless endoscopes to fibers that must be kept static. In this work we report a lensless endoscope which is exempt from the requirement of static fiber by designing and employing a custom-designed conformationally invariant fiber. We give experimental and theoretical validations and determine the parameter space over which the invariance is maintained.

We present a flexible, compact, and multimodal nonlinear endoscope (2.2 mm outer diameter) based on a resonantly scanned negative curvature hollow-core double-clad fiber. The fiber design allows distortion-less, background-free delivery of femtosecond and picosecond excitation pulses and the back-collection of nonlinear signals through the same fiber. Sub-micron spatial resolution together with large field of view is made possible by the combination of a miniature objective lens together with a silica microsphere lens inserted into the fiber core. We demonstrate coherent anti-Stokes Raman scattering, 2-photon fluorescence and second harmonic generation imaging at a rate of 10 frames/s.

International audience

International audience

International audience; We report the fabrication and characterization of the first double clad tubular anti-resonant hollow core fiber. It allows to deliver ultrashort pulses without temporal nor spectral distortions in the 700-1000 nm wavelength range and to efficiently collect scattered light in a high numerical aperture double clad. The output fiber mode is shaped with a silica microsphere generating a photonic nanojet, making it well suitable for nonlinear microendoscopy application. Additionally, we provide an open access software allowing to find optimal drawing parameters for the fabrication of tubular hollow core fibers.

Recently, there has been a surge in reports of so-called ‘lensless endoscopes’, a term which denotes the active control of the fiber injected wavefront from the proximal side only to enable imaging without any distal optics, thus allowing the miniaturization of the endoscope to the fundamental limit, the size of the optical fiber itself. Our approach sets itself apart in several ways: (i) the capability to perform nonlinear image contrast using two-photon fluorescence; and (ii) high image acquisition rates and (iii) the active control of the distal focused spot while bending the fiber. We have developed a multicore fiber (MCF) specifically for our approach. It consists of 169 homogeneous single-mode cores, each of which functions as one ‘pixel’ of the wave front. These fiber cores are spatially arranged in an aperiodic pattern to eliminate the satellite grating induced repliqua and to extend the field of view. The composite waveform at the distal end is then generated by pre-shaping the beam before it is coupled into the fiber cores. Hence, the generation of a focal spot and its scanning can be performed without any opto-mechanical components on the fiber tip. The MCF is designed with a multi-mode inner cladding with a very high numerical aperture (NA) of 0.65. This permits the collection of the resulting fluorescence signal with a high efficiency. A dedicated twist fiber design makes the developed imaging endoscope insensitive to fiber bending.

Multicore fiber bundles are attractive candidates for lensless endscopes because of their ruggedness and the relative simplicity involved in their calibration and operation. Nevertheless, the measurement of the transmission matrix of the MCF is still an interferometric process, typically requiring high stability and possibly sequential measurements. A key challenge is to replace this with a much simpler and robust technique – phase retrieval. In this talk, we will examine the major challenge in using phase retrieval in conventional MCFs. This is related to the discrete and periodic nature of the auto-correlation of an ordered MCF, resulting in the stagnation of phase retrieval algorithms in one of a multitude of local minimums. We employ phase diversity, i.e. more the one complex illumination pattern with a known phase profile can help overcome this issue. In particular, we identify that spiral phase patterns are well-suited due to their generation of complementary speckle patterns, resulting in highly non-redundant information. We experimentally demonstrate that three intensity images are sufficient to retrieve the transmission matrix with very high accuracy and success rates. Furthermore, we will also present a novel disordered MCF, which facilitates phase retrieval with a single intensity image and a priori knowledge of the core positions. This is a simple and rapidly converging method which relies on the aperiodic arrangement and the sparsity of the cores. Both these computationally inexpensive techniques highlight the potential of phase retrieval as a tool for robust phase calibration of fiber bundles in lensless imaging.

A class of miniaturized imaged systems based on multicore fibers (MCFs) and wavefront shaping, also known as lensless endoscopes, have emerged as promising candidates for non-invasive imaging deep inside the tissue. At the current stage of their development, these systems already provide features like pixelation-free wide-field and point-scanning imaging and are compatible with the majority of nonlinear imaging techniques, offering diffraction-limited resolution over a field of view only limited by the single fiber numerical aperture. Widely spaced single-mode cores in such an MCF are designed for very weak inter-core coupling, which ensures an infinite memory effect and provides good ultrashort pulse delivery framework for nonlinear imaging. In a true endoscopic setting, however, where the fiber geometry is subject to continuous deformation (at a rate from several Hz to several tens of Hz), results in inter-core phase and group delay dispersion (GDD) that changes as the fiber bends. This consequently degrades the PSF in terms of size and power in the focal spot, eventually rendering impossible to produce non-linear imaging. We addressed this issue by implementing an active measurement and compensation loop at the proximal end of an MCF, allowing to correct in real time the GDD changes and to minimize the temporal dispersion of the delivered laser pulses. We evaluate this approach against a passive scheme where a static pre-compensation is used in a compliment with a specifically designed MCF, allowing to drastically increase the MCF bending robustness.

Lensless endoscopes have generated a great deal of interest in the development of minimally invasive probes for imaging in sensitive and hitherto inaccessible regions as found in deep brain imaging. Lifting the requirement for the opto-mechanical elements at the distal end of the fiber reduces the footprint of the endoscope down to the fundamental limit, the fiber itself. Our approach, using specially designed multicore fibers allows us to i) generate two-photon fluorescence contrast with femtosecond pulses, ii) image at high speeds with resonant scanners, iii) simple and non-interferometric calibration schemes and iii) exhibits a high resilience to spatio-temporal distortion of the focus due to fiber bending. In this contribution, we will discuss how novel designs of the MCFs can lift several of the instrumental complexity typically associated wavefront shaping and high speed imaging. We show that the use of sparse arrays of fiber cores can provide pixelation-free imaging with no artifacts when employed in the wavefront domain as opposed to conventional fiber bundles. Furthermore, we examine the unique properties of the MCFs which allow for fast and non-interferometric calibration schemes and can tolerate severe bending with an intact focus. The inclusion of a secondary cladding on the MCF allows us high sensitivity detection though the fiber (NA = 0.6) whilst preserving the advantages of a sparse MCF. The combination of these new developments brings us towards the application of these ultrathin probes in realistic imaging conditions.

A simple technique for far-field single-shot non-interferometric determination of the phase transmission matrix of a multicore fiber with over 100 cores is presented. This phase retrieval technique relies on the aperiodic arrangement of the cores., Submitted to Optics Letters

International audience; We report two-photon lensless imaging through a novel golden spiral multicore fiber. This unique layout optimizes the sidelobe levels, field of view, cross-talk, group delay and mode density to achieve a sidelobe contrast of atleast 10.9 dB. We demonstrate experimentally the ability to generate and scan a focal point with a femtosecond pulse and perform two-photon imaging.

We present our recent progress in developing a two-photon lensless endoscope based on ultrathin multicore fiber and wavefront shaping. We discuss the field-of-view extension, intrinsic group delay compensation and bending compensation in such devices with the aim of imaging the deep brain with minimal invasion.

The periodic arrangement of core positions in multi-core fiber bundles introduces ‘ghost’ artifacts to endoscopic images obtained through them, whether in wide-field imaging (based on either direct imaging or speckle correlations) or in confocal scanning microscopy using wavefront shaping. Here we introduce partially disordered multi-core bundles as a means to overcome these artifacts. The benefits of their use will be discussed in the context of multiphoton scanning microscopy utilizing a spatial light modulator in the proximal end, and in the more general case of widefield imaging. We also show that both numerically and experimentally that the presence of disorder also enables to apply phase retrieval methods to characterize the phase distortion introduced due to propagation in the bundle without the need of an interferometrically stabilized reference. Thus, in addition to overcoming the challenge of ghost artifacts, disordered multi-core fibers have the potential to overcome another challenge, movement-induced phase distortions, by enabling real-time characterization of this phase distortion in reflection mode only via the proximal end.

International audience; 10 11 Multicore fiber bundles are widely used in endoscopy due 12 to their miniature size and their direct imaging capabilities. 13 They have recently been used, in combination with spatial 14 light modulators, in various realizations of endoscopy with 15 little or no optics at the distal end. These schemes require 16 characterization of the relative phase offsets between the 17 different cores, typically done using off-axis holography, 18 thus requiring both an interferometric setup and, typically, 19 access to the distal tip. Here we explore the possibility of 20 employing phase retrieval to extract the necessary phase in-21 formation. We show that in the noise-free case, disordered 22 fiber bundles are superior for phase retrieval over their peri-23 odic counterparts, and demonstrate experimentally accurate 24 phase information for up to 10 simultaneously illuminated 25 cores. Thus, the phase retrieval is presented as a viable al-26 ternative for real-time monitoring of phase distortions in 27 multicore fiber bundles. Endoscopy is a powerful tool used to image hollow organs with-32 out the need for surgery [1]. Miniaturization of the endoscope 33 probe will allow for a wider range of accessible organs to be 34 examined and, thus, is crucially important for applications. 35 Some miniature endoscopes are based on a single-mode optical 36 fiber which is mechanically scanned [2,3] or spectrally spread at 37 the distal end [4,5]. The use of a single-mode fiber circumvents 38 distortions due to propagation within the fiber. Yet, for minia-39 turization purposes, it is generally desirable to minimize the 40 number of elements at the distal end of the endoscope [6]. 41 Indeed, various techniques have been suggested for endoscopic 42 imaging where all the active elements are in the proximal end of 43 the fiber. Recent implementations are typically based on multi-44 mode optical fibers [7-9], GRIN fibers, or bundles of single-45 mode fibers [10-13]. In all these, light propagation through the 46 device, reflected in relative phase accumulated by the various 47 modes propagating through the optical system (which is also 48 dependent on bending and temperature) has to be taken into 49 account. Confocal scanning endoscopy, circumventing the 50 need to account for the accumulated phase, was performed ei-51 ther by using multi-core fiber (MCF) bundles or by using 52 GRIN fibers while scanning a confocal pinhole (or an input 53 single-mode fiber) at the proximal end [14]. The use of speckle 54 correlations and the "memory effect" in multicore fiber bundles 55 have also been recently suggested as a means to perform either 56 scanning endoscopy [15] or wide-field imaging [16] without 57 the need to compensate for the differences in the phase intro-58 duced by the different cores. Active phase compensation is, 59 however, by far the most direct and efficient approach to ad-60 vanced endoscopy applications. 61 Indeed, following the dramatic advances in spatial light 62 modulation technology, active compensation of the phase dis-63 tortion due to propagation either in a multimode fiber [7-9] or 64 in a multicore fiber bundle [10-13] has been pursued in recent 65 years. This requires accurate characterization of the phase dis-66 tortion induced by propagation in the endoscope. In multi-67 mode fibers, the measurement of the fiber transmission 68 matrix is sufficient to perform widefield imaging [9,17]. In 69 multicore bundles, this reduces to the problem of characteriz-70 ing the phase delay within each core, which can then be com-71 pensated for via the use of a spatial light modulator (SLM) [18]. 72 Alternatively, using an SLM, it is possible to perform confocal 73 scanning by adding a combination of a linear and a parabolic 74 phase profile on top of the phase distortion correction [11]. 75 The latter approach is especially useful for multiphoton imag-76 ing [12]. In most of the above cases, off-axis holography or self-77 referenced interferometry, was used to characterize the phase 78 distortion. This requires a stable interferometric setup and usu-79 ally requires access to the distal end of the fiber, and is difficult 80 to implement for correction of time-dependent distortions. For 81 multicore bundles, it is also possible to separately characterize 82 the phase shift between individual pairs of cores [11] (which 83 can, in principle, even be done in backscattering mode, taking 84 advantage of the light reflected from the distal fiber end). This 85 is, however, a painstakingly slow process. Therefore, a rapid 86 characterization method for the time-varying phase distortion 1 Letter Vol. 42, No. 4 / /Optics Letters 1 0146-9592/17/040001-01 Journal

International audience; We examine the impact of fiber bends on ultrashort pulse propagation in a 169-core multicore fiber (MCF) by numerical simulations and experimental measurements. We show that an L-shaped bend (where only one end of the MCF is fixed) induces significant changes in group delays that are a function of core position but linear along the bending axis with a slope directly proportional to the bending angle. For U-and S-shaped bends (where both ends of the MCF are fixed) the induced refractive index and group delay changes are much smaller than the residual, intrinsic inter-core group delay differences of the unbent MCF. We further show that when used for point-scanning lensless endoscopy with ultrashort pulse excitation, bend-induced group delays in the MCF degrade the point-spread function due to spatiotemporal coupling. Our results show that bend-induced effects in MCFs can be parametrized with only two parameters: the angle of the bend axis and the amplitude of the bend. This remains valid for bend amplitudes up to at least 200 degrees.

International audience; Cavity optomechanical systems with an enhanced coupling between mechanical motion and electromagnetic radiation have permitted the investigation of many novel physical effects. The optomechanical coupling in the majority of these systems is of dispersive nature: the cavity resonance frequency is modulated by the vibrations of the mechanical oscillator. Dissipative optomechanical interaction, where the photon lifetime in the cavity is modulated by the mechanical motion, has recently attracted considerable interest and opens new avenues in optomechanical control and sensing. In this work we demonstrate an external optical control over the dissipative optomechanical coupling strength mediated by the modulation of the absorption of a quantum dot layer in a hybrid optomechanical system. Such control enhances the capability of tailoring the optomechanical coupling of our platform, which can be used in complement to the previously demonstrated control of the relative (dispersive to dissipative) coupling strength via the geometry of the integrated access waveguide.

We take stock of the progress that has been made into developing ultrathin endoscopes assisted by wave front shaping. We focus our review on multicore fiber-based lensless endoscopes intended for multiphoton imaging applications. We put the work into perspective by comparing with alternative approaches and by outlining the challenges that lie ahead.

We demonstrate pixelation-free real-time widefield endoscopic imaging through an aperiodic multicore fiber (MCF) without any distal opto-mechanical elements or proximal scanners. Exploiting the memory effect in MCFs the images in our system are directly obtained without any post-processing using a static wavefront correction obtained from a single calibration procedure. Our approach allows for video-rate 3D widefield imaging of incoherently illuminated objects with imaging speed not limited by the wavefront shaping device refresh rate., Comment: Published in Optics Letters

International audience

We investigate lensless endoscopy using coherent beam combining and aperiodic multicore fibers (MCF). We show that diffracted orders, inherent to MCF with periodically arranged cores, dramatically reduce the field of view (FoV) and that randomness in MCF core positions can increase the FoV up to the diffraction limit set by a single fiber core, while maintaining MCF experimental feasibility. We demonstrate experimentally pixelation-free lensless endoscopy imaging over a 120 micron FoV with an aperiodic MCF designed with widely spaced cores. We show that this system is suitable to perform beam scanning imaging by simply applying a tilt to the proximal wavefront., Comment: Submitted to Optics Letters

Optomechanical systems, in which the vibrations of a mechanical resonator are coupled to an electromagnetic radiation, have permitted the investigation of a wealth of novel physical effects. To fully exploit these phenomena in realistic circuits and to achieve different functionalities on a single chip, the integration of optomechanical resonators is mandatory. Here, we propose a novel approach to heterogeneously integrate arrays of two-dimensional photonic crystal defect cavities on top of silicon-on-insulator waveguides. The optomechanical response of these devices is investigated and evidences an optomechanical coupling involving both dispersive and dissipative mechanisms. By controlling the optical coupling between the waveguide and the photonic crystal, we were able to vary and understand the relative strength of these couplings. This scalable platform allows for an unprecedented control on the optomechanical coupling mechanisms, with a potential benefit in cooling experiments, and for the development of multi-element optomechanical circuits in the framework of optomechanically-driven signal-processing applications.

We report on optomechanical effects in 2D photonic crystal defect cavities coupled to integrated silicon waveguides of different widths. Mechanical modes are observed systematically on a chip scale. By tuning the excitation laser wavelength, we observe optical spring effects. We extract optomechanical coupling coefficients and demonstrate the dispersive and dissipative nature of optomechanical coupling. Their relative contribution can be controlled by modifying the access waveguide width, thereby paving the way for a control of optomechanical coupling on the wafer level.

Thirty-four patients suffering from various kinds of tumors, including metastasis, were treated by selective embolization with both spherical and cylindrical poly(2-hydroxyethyl methacrylate) [poly(HEMA)] particles and topical chemotherapy. Treatment of a patient with carcinoid metastases in the liver is discussed. Immediately after embolization, 5-fluorouracil, and later, doxorubicin and Lipiodol, were selectively infused into the tumorous tissue for approximately 1 week. Patient received four cycles of this infusion. Chemoembolization proceeded against the background of anticoagulant therapy using small doses of heparin or its low-molecular-weight analogue, dalteparin. This was followed by transcutaneous transhepatic portography and embolization. Finally, the tumor-feeding artery and portal vein were sealed by a hydrogel. After 1.5 months, the affected liver lobe was resected. Although 4 years from the beginning of treatment, the patient is still alive. Embolization with poly(HEMA) hydrogel particles in conjunction with an anticancer drug infusion via catheter is recommended as an efficient method of tumor treatment. The therapeutic effect has been shown to be a function of ischemia and slow local infusion of drug into the tumor, and systemic drug levels can be kept low.

We investigate the non-linear mechanical dynamics of a nano-optomechanical mirror formed by a suspended membrane pierced by a photonic crystal. By applying to the mirror a periodic electrostatic force induced by interdigitated electrodes integrated below the membrane, we evidence superharmonic resonances of our nano-electro-mechanical system; the constant phase shift of the oscillator across the resonance tongues is observed on the onset of principal harmonic and subharmonic excitation regimes.

International audience; The polarization states of lasers are crucial issues both for practical applications and fundamental research. In general, they depend in a combined manner on the properties of the gain material and on the structure of the electromagnetic modes. In this paper, we address this issue in the case of solid-state organic lasers, a technology which enables one to vary independently gain and mode properties. Different kinds of resonators are investigated: in-plane microresonators with Fabry-Perot, square, pentagon, stadium, disk, and kite shapes, and external vertical resonators. The degree of polarization P is measured in each case. It is shown that although transverse electric modes prevail generally (P > 0), the kite-shaped microlaser generates negative values for P (i.e., a flip of the dominant polarization which becomes mostly transverse magnetic polarized). In general, we demonstrate that both the pump polarization and the resonator geometry can be used to tailor the polarization of organic lasers. With this aim in view, we, at last, investigate two other degrees of freedom, namely upon using resonant energy transfer and upon pumping the laser dye to a higher excited state. We then demonstrate that significantly lower P factors can be obtained.

e14717 Background: Laparoscopic pancreaticoduodenectomy (LPDE) has become increasingly popular in the world and now is considered to be a technically feasible and safe procedure for patients with tumors of the head of the pancreas and the periampullare area. At the same time, according to the literature data, a lot of surgeons stop performing totally laparoscopic pancreaticoduodenectomy (TLPDE) after 5 – 15 procedures because of the difficulties of learning curve. Aim of thew study: to evaluate the learning curve of totally laparoscopic pancreaticoduodenectomy. Methods: The data of 43 patients who were planed for LPDE during 5 year were analyzed. All the procedures were performed by one surgical team. 35 patients underwent totally laparoscopic pancreaticoduodenectomy (TLPDE). For 8 patients the procedures were palliative or converted. Patients were divided in three groups. Group A, B and C – 12;12;11 patients respectively. Operative time, intraoperative blood loss and the level of postoperative morbidity were examined. Results: Among the 43 patients, 35 patients underwent TLPDE. The conversion rate was in the group A - 33% (4 patients), group B – 33%(4 patients) and group C – no conversions. Mean operative time of TLPDE for the group A was - 542min; group B – 542min and group C less than 360min, minimally - 280). Mean blood loss was for group A - 683ml, group B – 612ml and group C 250ml. Total level of all kinds of postoperative morbidity was: group A - 66,5%, group B – 65,5% and group C – 36,0%. Postoperative mortality was: group A - 8,3%(one of the patients died from insufficiency of the pancreatojejenostomy, another – because of acute heart failure without any surgical complications); group B – 0% and group C - 0%. Conclusions: The results of TLPDE become significantly better after 25 procedures. The most difficult and potentially dangerous for intra and postoperative complications were: dissection along superior mesenteric and portal vein and suturing of pancreaticojejuno anastomosis. Performing TLPDE by the same team, including nurses, is a very important factor for quick learning curve and safety.

We take stock of the progress made into developing fiber-optic ultra-thin endoscopes assisted by wave front shaping. We focus on multi-core fiber-based lensless endoscopes intended for multi-photon imaging. We put the work into perspective and outline remaining challenges.

International audience

International audience