Pedro Moreno Zarate

Los productos cárnicos procesados, como los embutidos, incluidas las salchichas y las hamburguesas, forman parte importante de la alimentación cotidiana de muchas familias mexicanas debido a su practicidad, bajo costo y amplia aceptación cultural.

Active packaging is a new generation of packaging that, unlike traditional packaging, allows the preservation of food, not only contains it. Active packaging interacts with the food and the environment and, through different mechanisms, prevents its deterioration. These packages contain substances such as oxides, acids, alcohols, peptides, polyphenols, polysaccharides and fatty acids that can absorb or emit gases, regulate humidity, maintain temperature and act as antioxidants and antimicrobials. Within this group of container, smart packaging and edible coatings can be included. The smart packaging contains sensors that provide information on the presence or absence of a substance and others reflect the temperature, freshness and maturation of the food. The coatings, for their part, act as a barrier to gases and can integrate antioxidant and antimicrobial substances that prevent food deterioration. The purpose of this chapter is to provide a general description of active packaging, briefly explaining the different systems under which they work, the substances and the principles on which they are based, their applications, advantages and disadvantages.

Fs-laser induced element redistribution (FLIER) has been a subject of intensive research in recent years. Its application to various types of glasses has already resulted in the production of efficient optical waveguides, tappers, amplifiers and lasers. Most of the work reported on FLIER-based waveguides refers to structures produced by the cross-migration of alkali (Na, K) and lanthanides (mostly La). The latter elements act as refractive index carrying elements. Herein, we report the production of Ba-based, FLIER-waveguides in phosphate glass with an index contrast > 10⁻². Phosphate glasses modified with the same amount of Na₂O and K₂O, and variable amounts of BaO and/or La₂O₃ were used to produce the FLIER-waveguides with Ba and or La acting as index carriers. Ba-only modified glasses show a waveguide writing threshold and light guiding performance comparable to that of La-based structures. However, mixed Ba-La glasses show a much higher element migration threshold, and much smaller compositionally modified regions. This behavior is consistent with a competition effect in the cross-migration of both elements (Ba and La) against the alkalis. Such an effect can be applied to inhibit undesired element redistribution effects in fs-laser processing applications in multicomponent glasses.

Here in we present the fabrication and performance of waveguide tapers produced by femtosecond laser induced element redistribution in modified phosphate glasses. More particularly, it is demonstrated that by controlling the scan velocity during the writing process it is possible to adequately tune both the size of the modified area and the refractive index contrast to produce waveguides that can cope with mode field diameters in the range of 7-16 μm. In addition, we fabricated tapered structures through the induction of an acceleration in the laser scanning velocity, resulting in a device that can efficiently convert a wide range of mode fields. The fine control achieved over the index contrast in the range of 10 ^-3 and 10 ^-2 would allow the production of a wide variety of tapers that could potentially be used to couple numerous photonic devices.

The local modification of the composition of glasses by high repetition femtosecond laser irradiation is an attractive method for producing photonic devices. Recently, the successful production of waveguides with a refractive index contrast (Δn) above 10⁻² by fs-laser writing has been demonstrated in phosphate glasses containing La₂O₃ and K₂O modifiers. This large index contrast has been related to a local enrichment in lanthanum in the light guiding region accompanied by a depletion in potassium. In this work, we have studied the influence of the initial glass composition on the performance of waveguides that are produced by fs-laser induced element redistribution (FLIER) in phosphate-based samples with different La and K concentrations. We have analyzed the contribution to the electronic polarizability of the different glass constituents based on refractive index measurements of the untreated samples, and used it to estimate the expected index contrast caused by the experimentally measured local compositional changes in laser written guiding structures. These estimated values have been compared to experimental ones that are derived from near field images of the guided modes with an excellent agreement. Therefore, we have developed a method to estimate before-hand the expected index contrast in fs-laser written waveguides via FLIER for a given glass composition. The obtained results stress the importance of considering the contribution to the polarizability of all the moving species when computing the expected refractive index changes that are caused by FLIER processes.

The measurement of the refractive index of optical waveguides is a difficult task that involves different methods, among which those based on the refracted near field determination (RNF) are likely the ones providing the best resolution. Still, most such methods lack spectral resolution, which impedes accessing the index dispersion of the waveguide, an essential parameter for many applications. In this work, the refractive index of channel waveguides produced by fs‐laser induced ion‐migration in a P₂O₅‐La₂O₃‐K₂O‐based glass is measured by imaging ellipsometry. Along with EDX compositional maps and guiding performance, the dispersion and refractive index maps of several waveguides are measured. The results confirm that, in this glass, waveguides are formed due to an enrichment in La in the topmost part of the laser‐excited region which is accompanied by the cross migration of K toward the region underneath. Interestingly, the index contrast of the waveguides shows a wavelength‐independent behavior for wavelengths above ≈600 nm. This indicates that in the compositional range analyzed, La³⁺ ions linearly contribute to the glass polarizability due to the relatively large mass of La³⁺ ions and the relatively small size of the isolated La‐polyhedra accommodated in the phosphate glass network.

Experimental and Theoretical Modelling of Waste Produced by the Marble Industry of Tepexi de Rodríguez

The modification of the glass composition by high repetition rate femtosecond (fs) laser pulse irradiation appears as a very attractive method for the production of photonic devices [1]. It has recently been shown that this mechanism enables producing refractive index changes, Δn>10 ^-2 , leading to the production of highly efficient, and controllable passive waveguides in P ₂ O ₃ -La ₂ O ₃ -K ₂ O-based glasses [2]. The index contrast (An) is caused by the enrichment of La ₂ O ₃ in the guiding region which is depleted in K ₂ O due to cross migration of both elements. Still, it has also been shown [3] that the guiding region is enriched in other lanthanides present in the glass (i.e. Er, Yb). This effect may be detrimental for the production of active devices. In this work we show that fs-laser induced ion-migration can similarly be used to produce high performance waveguide amplifiers and lasers. In fact, we show the feasibility of producing waveguides with different gain in the same glass sample by varying the writing parameters, increasing the flexibility of this technique in integrated photonics applications.