Lasers are widely used to align optics. In most cases a unique laser beam is enough for alignment of “open” optics as shown in Figure 1 and Figure2. However, there are cases where the optical set up does not allow the use of a single laser beam in one direction as for example in collinear mirrors (Figure 3). In this case a device with two laser beams travelling in opposite directions on the same axis is extremely useful for alignment of the optics in opposite directions.
This article describes the design, integration and alignment of a Dual-beam laser.
This post discusses how spectrograph features such as the resolving power and the “size” of its optical elements are affected when the spectrograph is linked to a telescope with an optical fibre.
The main aim of the post is to help in the design of a spectrograph taking into account the features of any given telescope together with the specifications of the required spectrograph. The basic parameters of a telescope are its size (aperture diameter), the focal ratio (F/#) and the average seeing at the observing location. For the spectrograph, on the other hand, the specifications are usually the required resolving power, the spectral range and the optical efficiency.
Injecting a laser beam into an optical fibre is a very common task in optical laboratories. For example it is extremely useful for the alignment and collimation of optical components in instruments like fibre-fed spectrographs. Our youtube video Injecting a laser beam into an optical fiber describes this process.
This article describes a simple laboratory spectroscopy test bench to obtain resolving powers as high as R = 150 000. The optical set up is basically composed of an échelle diffraction grating, a doublet achromatic lens, a beam splitter, an optical fibre and a CCD camera. Among others, this experiment allows to discern and study the longitudinal emission modes of diode lasers. Our 20′ video Building a spectroscopy high resolution experiment explains in details the bench implementation
The purpose of this post is to show the alignment procedure of an on-axis parabolic mirror. The methodology has been applied to align the collimator of two of our fibre linked spectrographs:
- LECHES which uses the full parabola and
- FLECHAS where the collimator works in an off-axis parabola. In this case we have used a full parabola because it is cheaper than a dedicated off-axis mirror.
An off-axis parabolic (OAP) mirror consists of a small section cut out from a larger, so-called “parent” parabolic mirror
We present here our based prism low resolution spectrograph baptized BESOS or BEst Simple Optical Spectrograph (kisses in spanish). Designed in 2003, the spectrograph was proposed to overcome the low throughput of our previous instrument LOROS (coming soon to this blog) which was an instrument based on an on-axis dispersion prism obtained from a commercial spectroscope. The total efficiency of LOROS was only 25% in the visible spectral range. BESOS was built with only two doublets and a prism. This configuration reached almost 87 % at 620 nm. With such efficiency and low resolution, we expected to measure the red shift of the most bright galaxies and quasars.
In this post we provide a description of the instrument, features, performances and the set of mechanical drawings.
Using just water and sugar in order to create a mixture with a gradient refraction index a laser beam can bent as shown in the video below.
- Youtube video: Bending a laser beam
This is the principle explaining the mirages, gradient index lenses and fibres. Amaze your friends by telling them that you put a black hole behind the recipient in order to create a huge gravitational field which bends light beams (General theory of relativity). A friend was convinced that we put a strong magnet below !!!
When properly poured, the sweet water will create a mixture with a gradual refraction index. The bottom will have a higher refraction index than the top. When a light beam travels inside, its direction will bend continuously (principle of Fermat)
In order to success the mixture:
- Saturate the water with sugar. You can go faster by heating the water
- Put FIRST the fresh water in the recipient and then the sweet water at room temperature. The saturated water will sink creating the gradient.
- Do NOT shake or mix the solution once you pour the sweet water
Bending a laser beam by CAOS group is licensed under a Creative Commons Attribution-Non-Commercial-No Derivative Works 3.0 Germany License.
Based on a work at spectroscopy.wordpress.com.