Nouvelles sur l’optique, la lumière,

la technologie d’analyse optique et plus

AM1.5 spectrum

Photochemistry: where light meets chemistry

Photochemistry is the discipline that studies the chemical processes in which light plays a role. In this post, we do not aim to carry out a thorough analysis about photochemistry, but to provide a brief overview about some concepts we find interesting in this field. In the first place, we are going to describe the basic operation of a solar simulator, which is employed to reproduce natural sunlight. Then, we will explain two different types of reactions: photodegradation, focusing on polymers; and photocatalysis, describing two photocatalytic reactions (water splitting and CO2 reduction).

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Infrared sources for researchers

Infrared light sources for researchers

The infrared spectral region is the part of the electromagnetic spectrum that covers from 700 nm to 1,000 µm. Within the infrared, usually three bands can be distinguished: near infrared (NIR, 780 nm – 3 µm), mid-infrared (MIR, 3 µm – 50 µm), and far infrared (FIR, 50 µm – 1,000 µm). There are several types of infrared source employed by researchers in their experiments, including halogen, LED, SLD, laser and globar sources. In this post, we explain their basic operation, as well as their characteristics and main applications.

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Mid-infrared fibers

Mid-infrared fibers are the ones that work in the 2 µm – 20 µm wavelength range, where silica fibers cannot be employed. There are several types, but in this post we are going to focus on two of them: fluoride fibers, which are made of several fluoride glasses, and hollow core fibers, in which the core is a hollow region. In particular, we are going to explain their main characteristics, including their advantages and weaknesses; as well as their applications, which can achieve high relevance in the next few years.

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Optical fiber manufacturing techniques

How are optical fibers made?

The optical fiber manufacturing process includes several steps: the preform production, the fiber draw and the performance tests. In this post, we will describe them, especially focusing on the preform fabrication. The preform is a solid glass rod that already has a core and a cladding, but their dimensions are far larger than in the final fiber. There are several techniques to produce the preform: 1) modified chemical vapor deposition (MCVD), 2) outside vapor deposition (OVD), and 3) vapor axial deposition (VAD).

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Myths and legends about glass: from the core of an optical fiber

Glass is a key material in optics and, in particular, in optical fibers, as they are usually made of silica, the most abundant mineral found on the surface of the Earth. In this post, we are going to focus on the properties of glass. In the first place, we will answer if glass is a solid or a liquid and describe how it is obtained, including some important concepts as the glass transition. Then, it will be explained why glass is used in optical fibers, as well as the main types of glass optical fibers.

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Introduction to quantum photonics

Quantum photonics is the practical application of quantum optics (the theoretical study of photons, which are the quantum of light) for the development of new technologies. Quantum photonics includes different fields such as quantum computing, quantum metrology and quantum cryptography. In this post, we provide a first approach to this domain in a simple way, describing some of its basic concepts, such as the qubit and some of its properties, like the superposition or the quantum entanglement.

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Branch detection in green beans using reflection spectroscopy

In this post we present an application case of spectroscopy in the fruits and vegetables industry. The combination of reflectance spectroscopy measurements in the visible and near infrared (NIR) spectrum and an artificial neural network is employed to distinguish between branches (foreign bodies, a relevant problem in the agrifood sector) and green beans for two different types of beans: round (Phaseolus vulgaris) and flat (Phaseolus coccineus). Good results are achieved, especially in the visible spectrum, demonstrating the potential of spectroscopy.

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Of light and plants

One of the first biology lessons we are taught in school is that plants need sunlight to perform photosynthesis to “feed” themselves and live. Nevertheless, the relationship between plants and light is more complex. In this post we will describe how different wavelengths, from ultraviolet to far red, are employed to control the growth or the flowering of plants.

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NIR spectroscopy and Machine Learning

Near infrared spectroscopy (NIR) is employed in the agrifood industry to recover information about the chemical composition and quality parameters of different products in a non-invasive, fast and accurate way. However, the relationships between the spectral measurements and the quality parameters are not trivial, and different machine learning methods are employed for modeling them. In this post, an overview of the commonly employed calibration methods based on machine learning will be provided.

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Scientific cameras for spectroscopy

With the increasing importance of hyperspectral and multispectral imaging, the use of cameras in spectroscopic applications has also grown. In this post we will describe the process by which a camera generates an image after being exposed to a light source as well as the main existing types of cameras (silicon-based CCDs, CMOS sensors and InGaAs sensors), including their characteristics, advantages and disadvantages.

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