Lasers laser pointers

Laser printers, bar code readers, unmanned freeway tollbooths, laser pointers—none of these very common devices would be possible ivithout laser technology. This is just a minor sampling the list of laser applications goes on and on. 

But there are other applications as well, such as recording and reading information. We see this at a grocery store, scanning bar codes on products. You also see laser pointers, which are used here in some of the lectures. All kinds of very simple things as well as very complex things. 

Semiconductor laser diodes are widely used in CD players, DVDs, printers, telecommunication or laser pointers. In the structure, they are similar to LEDs but they have a resonant cavity where laser amplification takes place. A Fabry-Perot cavity is established by polishing the end facets of the junction diode (so that they act as mirrors) and also by roughening the side edges to prevent leakage of light from the sides of the device. This structure is known as a homojunction laser and is a very basic one. Contemporary laser diodes are manufactured as double heterojunction structures. 

Laser molecular beam epitaxy, fabrication method for inorganic materials, 7 415t Laser photochemical vapor deposition (LPCVD), 19114-116 Laser pointers, 14 678 Laser-promoted dehydrohalogenation,... 

Cellular telephone base stations Radio towers Microwave towers Lasers (including laser pointers)... 

To point at an image, use a laser pointer or mouse-controlled pointer. Should you choose to point at the screen itself, be sure not to block the image. 

Visible spectra of Mg2 -Calmagite and free Calmagite at pH 10 in ammonia buffer. [From C. E. Dahm, J. W. Hal. and B. E. Mattioni, "A Laser Pointer-Based Spectrometer for Endpoint Detection of EDIA nrations. J. Chem. Ed. 2004,81. 1787.]... 

Young MA, Stuart DA, Lyandres O, Glucksberg MR, Van Duyne RP. Surface-enhanced Raman spectroscopy with a laser pointer light source and miniature spectrometer. Canadian journal of Chemistry 2004, 82, 1435-1441. 

The average intensity of sunlight hitting the surface in the continental U.S. at noon is about 200 W/m2. A typical laser pointer produces 5 mW in a 1 mm2 spot, so the intensity is about 5000 W/m2. At the opposite extreme, commercially available ultrafast laser systems can readily produce 100 mJ pulses with 100 fs duration (1012 W peak power). This peak power is roughly equal to the worldwide electrical generation capacity. Such pulses can be focused to about 10 1° m2 (1022 W/m2) still higher peak powers are created for specialized applications, such as laser fusion. 

A mole of photons is given the name einstein. A typical red laser pointer produces 5 mW average power at a wavelength A = 650 nm. How long does it take this pointer to produce one einstein ... 

Technology follows increasing dynamism and controllability, e.g. wooden pointer, to telescopic pointer, to laser pointer. 

Schematic of a semiconducting pn junction distributed Bragg59 reflector laser diode (or injection laser), such as used in 1-mW laser pointers (HeNe, 633 nm (obsolete) deep red AIGaAs 650 to 670 nm red-orange 635 nm frequency-doubled green 532 nm blue, 473 nm) and CD and DVD players (670 nm "Blue-Ray" InGaN 405 nm). The optically flat front surface (shown) is partially reflective ( 95%) the optically flat back surface (not shown here) is highly reflective ( 100%) and parallel to the front surface. The top and bottom electrical contacts provide the necessary external bias across the two semiconductor regions. The wavelength is determined by the distance between the two optically flat surfaces. The angular divergence of the output beam is considerable.

A 100-W immersion heater (such as VWR Scientific Inc. 33897-140 a 200-W to 300-W tea/coffee immersion heater can also be used), controlled by a Variac magnetic stirrer and stir bar 1000-mL beaker thermometer with a resolution of 0.02 K (platinum resistance thermometer or calibrated thermistor such as Vernier model TMP-BTA) 1- to 5-mW He-Ne laser (633 nm) or a red (545 mn) or green (532 nm) laser — a battery-operated laser pointer is suitable, but a module with a separate 3-volt power supply, available from Z-Bolt and other sources, will give better power stability for long rans two Polaroid sheets in rotation holders photodetector such as photomultiplier tube or Thorlabs model 201/579-7227 silicon photodiode analog-to-digital data collection system such as Vernier LabPro. 

The use of a doubled Nd YAG laser is particularly appealing, since this is becoming increasingly available as for example a relatively inexpensive green laser pointer. Figure 3 shows the overlap of the I2 absorption lines with the doubled output of a pulsed Nd YAG laser as its frequency was varied by tuning the temperature of a single frequency... 

These results demonstrate that nanostrucmred carbon materials can be evaporated or undergo phase changes/transformations upon laser excitation of significantly lower intensity compared to bulk materials. Even the power of laser pointers commonly used during conference presentations or in the class room (up to 100 mW) is enough to heat carbon samples up to 3,500°C, evaporate and redeposit graphitic nanocarbons or convert nanodiamond into carbon onions, when focused to a spot size of several micrometers. 

Lasers have become increasingly important in various applications. They can be found in laser printers, CD/DVD writers and players, scanners, laser pointers, control instruments, and scientific equipment. Furthermore, various kinds of... 

LPL-30 Pointing Laser Long Range Laser Pointer... 

Afterimage - A reverse contrast, shadow image left in the visual field after a direct exposure to a bright light, such as a laser pointer. 

The Institute for Chemical Education at the University of Wisconsin [5] offers slides that allow one to illustrate the optical interference in the classroom. When a laser pointer is passed through the transform on the slide the diffraction pattern is observed. By changing the color of the laser the effect of wavelength can be demonstrated. The effect of patterns in the transform can readily be seen in the diffraction. This is a very useful way to illustrate how diffraction works beyond Bragg s Law. 

Definitely. Many lasers used in modern chemistry laboratories are powerful enough to cause a person to go blind after only a fraction of a second of direct exposure to the eye. Some are even so powerful that they can burn or ignite objects placed in their path. Laser pointers you can buy in the store are not this powerful, however, so you don t have to worry about a laser you personally own being quite this dangerous. You should still definitely avoid shining them in your eye, though, because they can be damaging. 

This requires a laser pointer and a CD. Observe safety precautions do not aim the laser beam at anyone s eyes. Aim it, at approximately normal incidence, at the side of the CD that appears silvered. When the beam hits the tracks near the centre of the disc, a diffraction pattern is created (Fig. 1.10). This pattern is a two-dimensional analogue of X-ray diffraction from a three-dimensional crystal. 

Figure 1. 10 Diffraction pattern from a laser pointer, when shown on the track near the end of a music CD the direct reflection has the cross pattern.

A laser diode is a laser where the active medium is a semiconductor similar to that found in a hght-emitting diode. Laser diodes are used in devices for optical storage, laser pointers, and fiber optics. 

---