Category Archives: Laboratory

Simulated White Laser: a tool for optical alignment

Introduction

A way to simulate a white laser is to combine three lasers: red, green and blue. The superposition of the three colors gives the appearance a of a white laser.

Our basic motivation to make such a device is to have a practical tool to align optical systems such as spectrographs, optical setups and measurements of optical efficiency.

Continue reading

Leave a comment

Filed under Laboratory

FLECHAS Opto-mechanical Components

FLECHAS is a breadboard Echelle spectrograph. Its name stands for Fiber Linked ECHelle Astronomical Spectrograph.

The article is aimed to distribute, with as much detail as possible, each FLECHAS subsytem and their components. With the help of the document Integration and alignment of FLECHAS we believe you are in the best condition to build your own breadboard spectrograph.

Good luck!

The CAOS team.

Continue reading

3 Comments

Filed under Laboratory, Spectrographs

Dual-laser beam

Introduction:

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.

Continue reading

Leave a comment

Filed under Laboratory

Injecting a laser beam into an optical fibre

Introduction.

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.
Continue reading

1 Comment

Filed under Laboratory

Building a spectroscopy high resolution experiment

Introduction

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

Continue reading

Leave a comment

Filed under Laboratory

Alignment of an on-axis parabolic mirror

Introduction:

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
Continue reading

Leave a comment

Filed under Laboratory

Bending a laser beam

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:

  1. Saturate the water with sugar. You can go faster by heating the water
  2. Put FIRST the fresh water in the recipient and then the sweet water at room temperature. The saturated water will sink creating the gradient.
  3. Do NOT shake or mix the solution once you pour the sweet water

Creative Commons License
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.

3 Comments

Filed under Laboratory

Measuring transmission for Canon objectives

Purpose

Till present we have used several different Canon objectives as cameras on our spectrographs:

  • Canon EF 200mm 1:2.8 L II USM objective, for FLECHAS/standard.
  • Canon EF 100mm 1:2.0 USM objective, for FLECHAS/Jena.

The article presents our experimental results with the calculation of the transmission for these objectives.

Continue reading

Leave a comment

Filed under Laboratory

Optical efficiency of Newport transmission gratings

Introduction

We present here the the optical efficiency (transmission vs. wavelength) for its 1st order for two of Newport (former Richardson gratings) transmission gratings:

  • Ref. 54-006-630R, 200lin/mm, blazed 10.0 deg @505nm, 58x58x10mm
  • Ref. 54-006-806R 300lin/mm, blazed 14.6 deg @490nm,  58x58x10mm

and a description of the laboratory set-up to take these measurements.

Continue reading

1 Comment

Filed under Laboratory

Assembling a fibre with SMA connectors

Purpose

In this post we want to show through pictures and drawings the process of assembling a bare fibre into a protective jacket and ended with commercial connectors for spectroscopy purposes. In particular, we have prepared a 10m, 50μm core fibre with SMA connectors and protected with a  square-locked stainless steel tube.

Continue reading

5 Comments

Filed under Laboratory