Green Laser Pointer Research Articles

Rapid reversible phototuning of lasing frequency in dye-doped cholesteric liquid crystal.

Lasing in induced cholesteric liquid crystal (CLC) containing highly photosensitive azo chiral dopant (ChD) and pyrromethene laser dye was investigated. Due to the absence of excitation energy transfer from the dye molecules to the molecules of ChD in such a system, a low lasing threshold was achieved. When using violet and green light-emitting diodes, reversible frequency tuning was obtained in the range of about 30 nm with a tuning time 1-2 orders of magnitude smaller than in conventional CLC laser systems based on azo and azoxy photosensitive compounds. Further increase of the intensity of the excitation light by using a green laser pointer allowed us to achieve a record phototuning speed (∼21 nm in 148 ms).

Spectral cola or how to turn green laser light red

A green laser pointer shone through a glass of cola will appear red when looking from above the glass. Lowering the laser so that it is deeper in the cola, the colour will vary from orange to deep red. Fluorescence and absorption spectra were recorded consistent with the reddening of the laser. The depth dependence of the colour of the immersed laser is attributed to a more significant absorption of the short wavelengths by the cola, making the laser look redder as it is lowered deeper into the cola. To confirm this hypothesis, we simulated the fluorescence spectrum we would get at various depths by applying the Lambert law on our measured fluorescence spectrum. These spectra were then converted into red, green and blue (RGB) values. These values were compared to those measured on images of the immersed laser beam at corresponding depths.

Spectral-domain optical coherence tomography and fundus autofluorescence findings in a case of laser pointer-induced maculopathy.

To describe the spectral-domain optical coherence tomography and fundus autofluorescence findings in a case of laser pointer-induced maculopathy. Observational case report of a patient with bilateral decreased visual acuity after exposure to a handheld green laser pointer. A 15-year-old boy presented with decreased vision after exposure to a green laser pointer. Fundoscopy revealed gray and yellowish round spots in the foveal area of both eyes. Fundus autofluorescence imaging revealed subtle changes of the normal background macular autofluorescence of the right eye, with hyperautofluorescence dots in the fovea of the left eye. Spectral-domain optical coherence tomography showed a variety of changes of the outer retina and retinal pigment epithelium, with disruption of the external limiting membrane, the photoreceptor ellipsoid zone of the inner segments, and the interdigitation zone in the foveal region in both eyes. Six months after laser exposure, fundoscopic examination showed persistent alterations at the level of the retinal pigment epithelium in the fovea in both eyes. Fundus autofluorescence revealed mild but persistent changes of the normal autofluorescent macular background in both eyes. Spectral-domain optical coherence tomography showed partial resolution of the outer retinal disruption noted on his initial visit with persistent, small foveal photoreceptor defects in both eyes. Laser pointer maculopathy may disturb the outer retinal architecture in a manner evident on spectral-domain optical coherence tomography and fundus autofluorescence, resulting in decreased visual acuity. Proper warnings should accompany these devices and access to them by minors should be limited.

Detection of explosives and latent fingerprint residues utilizing laser pointer–based Raman spectroscopy

A modular, compact Raman spectrometer, based on a green laser pointer, was developed and applied for point detection. Its capabilities together with the portability that it offers make it a potential candidate for field applications.

Bilateral macular injury from a green laser pointer

We report the case of a 13-year-old boy who had a bilateral macular injury after playing with a green laser pointer for a duration of 1 minute. Clinical examination revealed a decrease in visual acuity and macular injury in both eyes, and imaging investigations revealed a bilateral macular lesion due to exposure to the laser pointer. At 3 months’ follow up, visual function had improved but remained partially impaired. This case emphasizes the importance of cautious and appropriate use of laser pointer devices because of the potential vision-threatening hazards induced by mishandling of these devices.

10m/500Mbps WDM visible light communication systems

A wavelength-division-multiplexing (WDM) visible light communiction (VLC) system employing red and green laser pointer lasers (LPLs) with directly modulating data signals is proposed and experimentally demonstrated. With the assistance of preamplifier and adaptive filter at the receiving sites, low bit error rate (BER) at 10 m/500 Mbps operation is obtained for each wavelength. The use of preamplifier and adaptive filter offer significant improvements for free-space transmission performance. Improved performance of BER of <10(-9), as well as better and clear eye diagram were achieved in our proposed WDM VLC systems. LPL features create a new category of good performance with high-speed data rate, long transmission length (>5m), as well as easy handling and installation. This proposed WDM VLC system reveals a prominent one to present its advancement in simplicity and convenience to be installed.

Laser pointer induced macular damage: case report and mini review

To report laser pointer induced damage to retina and choroid and briefly review literature. A case report of a 13-year old Caucasian boy developed blurry central vision and central scotoma in right eye (OD). He was exposed for one minute to class IIIA green laser pointer of 650 nm wavelength and 5 mW power. Clinical examination showed a grayish lesion in foveal region. Ancillary testing revealed disruption of the retinal pigment epithelial (RPE) layer in foveal region and indocyanine green angiography demonstrated evidence of choroidal hypofluorescence suggestive of choroidal infarction in OD. Visual acuity improved from 20/100 to 20/60 in one day and he was treated with tapering doses of oral prednisolone (40 mg) for 3 weeks. Laser pointer with a power of >5 mW caused damage to RPE in the macula. Children should not be given laser pointers as toys especially those with label of danger instructions.

Increasing Student Understanding of Microscope Optics by Building and Testing the Limits of Simple, Hand-Made Model Microscopes

The ability to effectively use a microscope to observe microorganisms is a crucial skill required for many disciplines within biology, especially general microbiology and cell biology. A basic understanding of the optical properties of light microscopes is required for students to use microscopes effectively, but this subject can also be a challenge to make personally interesting to students. To explore basic optical principles of magnification and resolving power in a more engaging and hands-on fashion, students constructed handmade lenses and microscopes based on Antony van Leeuwenhoek's design using simple materials-paper, staples, glass, and adhesive putty. Students determined the power of their lenses using a green laser pointer to magnify a copper grid of known size, which also allowed students to examine variables affecting the power and resolution of a lens such as diameter, working distance, and wavelength of light. To assess the effectiveness of the laboratory's learning objectives, four sections of a general microbiology course were given a brief pre-activity assessment quiz to determine their background knowledge on the subject. One week after the laboratory activity, students were given the same quiz (unannounced) under similar conditions. Students showed significant gains in their understanding of microscope optics.

Visible-Light-Assisted HCHO Gas Sensing Based on Fe-Doped Flowerlike ZnO at Room Temperature

In this work, Fe-doped flowerlike ZnO powders with various doping contents were successfully fabricated by a hydrothermal method. The results of X-ray diffraction and UV–vis DRS spectra revealed that the Fe ions have been successfully doped into the crystal lattice of the ZnO host structure, and the optical absorption response of Fe-doped ZnO was extended into the visible region for the incorporation of Fe ions. The room-temperature photoelectric gas sensing of formaldehyde (HCHO) based on the Fe-doped ZnO was also studied under 532 nm light irradiation provided by a green laser pointer. It was found that the as-prepared Fe-doped ZnO samples showed excellent sensitivity, in which the gas response to 5 and 100 ppm formaldehyde can reach to 22% and 287% under 532 nm light irradiation at room temperature, respectively. The sensing mechanism of the obvious visible-light-induced photoelectric gas sensing was discussed with the help of surface photovoltage measurement. Our results demonstrated that visible light irradiation was a promising approach to achieving a large response for gas sensors at room temperature. This work will pave a way for the development of a low-cost practical gas sensor.

A case of retinal light damage by green laser pointer (Class 3b)

A case of retinal light damage by green laser pointer (Class 3b)

Inexpensive Raman Spectrometer for Undergraduate and Graduate Experiments and Research

We describe the construction and performance of an inexpensive modular Raman spectrometer that has been assembled in the framework of a fourth-year undergraduate project (costs below $5000). The spectrometer is based on a 4 mW 532 nm green laser pointer and a compact monochromator equipped with glass fiber optical connections, linear detector array, and a USB computer connection and power supply. Because of its backscattering geometry, the spectrometer can be used for liquid and solid samples and offers a spatial resolution below 100 μm. With a spectral resolution of ca. 20 cm−1, accuracy of 2 cm−1, and a cutoff wavenumber below 340 cm−1, the Raman spectrometer has useful specifications. The apparatus is compact and portable. In conjunction with a laptop computer, it can be operated on batteries and would thus be suitable for field measurements. All components of the spectrometer are easily visible and accessible, which makes it ideally suited for lecture and teaching lab demonstrations unlike conventional “black box” instruments. We use this spectrometer for various undergraduate and graduate experiments and research, for analytical applications (e.g., determining alcohol content of beverages or purity of aspirin), and fundamental research (e.g., hydrogen bonding in solid aspirin or liquid water and temperature-dependence of the OH-stretching Raman band of liquid water).

Green Diode Laser Pointers Have Now Dropped in Cost to About $10

Also on the cheap apparatus hunt, handheld green diode laser pointers are now $8–12 each from www.amazon.com or www.ebay.com—search for “green laser pointers.” Because green light is in the center of the sensitivity of our eyes, we see 5 mW of green light MUCH more clearly than the same power red diode laser. Green lasers are preferred for pointing out astronomical objects in the night sky or for those faint wave diffraction experiments. A group of my students worked on green laser pointer diffraction experiments this past summer, and their work can be seen at http://physicsed.buffalostate.edu/eurp09.

A Case of Green Laser Pointer Injury to the Macula

Purpose: We report a case of macular injury by accidental exposure to a green laser pointer. Case summary: A 25-year-old man had an acute reduction of visual acuity in his right eye two years ago after accidental exposure to a green laser pointer for a few seconds. The patient’s best corrected visual acuity was counting fingers in his right eye. Fundus examination and optical coherence tomography showed a macular hole and a linear retinal scar in his right eye. Conclusions: Green laser pointers may cause macular damage after exposure of just a few seconds, which can lead to irreversible reduction of visual acuity.

Evaluation of a green laser pointer for flow cytometry

Flow cytometers typically incorporate expensive lasers with high-quality (TEM00) output beam structure and very stable output power, significantly increasing system cost and power requirements. Red diode lasers minimize power consumption and cost, but limit fluorophore selection. Low-cost DPSS laser pointer modules could possibly offer increased wavelength selection but presumed emission instability has limited their use. A $160 DPSS 532 nm laser pointer module was first evaluated for noise characteristics and then used as the excitation light source in a custom-built flow cytometer for the analysis of fluorescent calibration and alignment microspheres. Eight of ten modules tested were very quiet (RMS noise < or = 0.6% between 0 and 5 MHz). With a quiet laser pointer module as the light source in a slow-flow system, fluorescence measurements from alignment microspheres produced CVs of about 3.3%. Furthermore, the use of extended transit times and < or =1 mW of laser power produced both baseline resolution of all 8 peaks in a set of Rainbow microspheres, and a detection limit of <20 phycoerythrin molecules per particle. Data collected with the transit time reduced to 25 micros (in the same instrument but at 2.4 mW laser output) demonstrated a detection limit of approximately 75 phycoerythrin molecules and CVs of about 2.7%. The performance, cost, size, and power consumption of the tested laser pointer module suggests that it may be suitable for use in conventional flow cytometry, particularly if it were coupled with cytometers that support extended transit times.

Laser-Induced Fluorescence in Gaseous I2 Excited with a Green Laser Pointer

The use of a green laser pointer to excite fluorescence in gaseous I2 results in an unexpected behavior: on transiting the cell, the beam alternately appears brightly and vanishes completely. This behavior is attributed to temporal changes in the laser’s operating wavelength, likely due to temperature changes of the optical cavity as it warms up under power. As a result, the laser tunes itself into and out of resonance with the I2 absorption lines in the region of the laser gain profile. For this explanation to hold, it is also necessary that the laser operate with relatively high spectral purity, meaning a small number of narrow lasing modes. Spectra recorded for several different pointers display widely varying properties: some pointers operate on a single mode much of the time, while others emit in many weak lines in addition to one or two strong ones. Green laser pointers and an Ar-ion laser are used together to excite gaseous I2, illustrating in a comprehensive way the conditions necessary for lase...

Evidence for Specificity in Lipid-Rhodopsin Interactions

The interaction of bovine rhodopsin with poly- and monounsaturated lipids was studied by (1)H MAS NMR with magnetization transfer from rhodopsin to lipid. Experiments were conducted on bovine rod outer segment (ROS) disks and on recombinant membranes containing lipids with polyunsaturated, docosahexaenoyl (DHA) chains. Poly- and monounsaturated lipids interact specifically with different sites on the rhodopsin surface. Rates of magnetization transfer from protein to DHA are lipid headgroup-dependent and increased in the sequence PC < PS < PE. Boundary lipids are in fast exchange with the lipid matrix on a time scale of milliseconds or shorter. All rhodopsin photointermediates transferred magnetization preferentially to DHA-containing lipids, but highest rates were observed for Meta-III rhodopsin. The experiments show clearly that the surface of rhodopsin has sites for specific interaction with lipids. Current theories of lipid-protein interaction do not account for such surface heterogeneity.

Retinopathy From a Green Laser Pointer

To report retinopathy following exposure to light from a commercially available class 3A green laser pointer. A 55-year-old woman with a ring melanoma was scheduled for enucleation. The eye (visual acuity 20/20) had a healthy-appearing macular retina. The retina was exposed to light from a commercially available class 3A green laser: 60 seconds to the fovea, 5 minutes to a site 5 degrees below the fovea, and 15 minutes to a site 5 degrees superior to the fovea. Color photographs were obtained before and after exposure. The eye was enucleated 20 days after exposure. Laser power measurements averaged less than 5 mW. Retinopathy was observed 24 hours after laser exposure. This was characterized by a yellowish discoloration at the level of the retinal pigment epithelium (RPE) in the subfoveal region and at the site superior to the macula where the retina received 15 minutes of laser exposure. Each site developed granular changes at the level of the RPE within 5 days of exposure. Histologic study showed RPE damage in the exposed subfoveal and parafoveal regions. A class 3A green laser pointer caused visible retinopathy in the human eye with exposures as short as 60 seconds.

A Comparison of the Suitability of Alizarin Red S and Calcein for Inducing a Nonlethally Detectable Mark in Juvenile Guppies

Mark–recapture studies are an important component of fisheries research. A diversity of marks is needed to meet the demands of experimental designs and to overcome species-specific variation in marking success. Suitable marks must not alter the viability of marked individuals, must be easy to detect, and must be retained for an appropriate period of time. I compared the effect of alizarin red S and calcein on the individual growth and mortality rates of guppies Poecilia reticulata via short-term experiments (<14 d) conducted both in environments where alizarin- and calcein-marked fish were allowed to interact with unmarked fish and in environments where fish were segregated by mark. Neither mark affected the growth or mortality of marked individuals. Both marks were easily applied, did not affect the appearance of fish, and could be detected on the skeleton of live, anesthetized fish or ethanol-preserved specimens without the additional preparation (or lethality) involved in detecting marks on otoliths. However, both marks were subject to fading with time and when fish were exposed to high water temperatures or to direct sunlight. Thus, pilot experiments should be conducted under field conditions before marks are used for long-term mark–recapture studies. I also present an inexpensive and portable technique for detecting alizarin that uses a green laser pointer as the excitation source. This alizarin detector performed as well as a portable calcein detector (Leips et al. 2001) and could easily be modified for improved performance. Alizarin red S and calcein fluoresce at different wavelengths, so both marks can be used simultaneously in studies examining multiple treatment groups or cohorts. The use of alizarin red S may be preferred to that of calcein because its red fluorescence is more easily distinguished from the autofluorescence of bone.

Surface-enhanced Raman spectroscopy with a laser pointer light source and miniature spectrometer

The initial steps toward a miniature, field portable sensor based on surface-enhanced Raman spectroscopy (SERS) are presented. It is demonstrated that a low-cost miniaturized Raman system can be used in place of a larger, higher-cost conventional Raman system. This system was developed by sequentially replacing components of a laboratory scale Raman spectroscopy system with smaller, lower-cost, commercially available components. For example, a green laser pointer was used as the excitation source, a reflectance probe fiber-optic cable was used for laser delivery and collection, and a compact card-based spectrometer was used for dispersion and detection. Spectra, collected with the laser pointer Raman system, are presented of a resonant (Rhodamine 6G) and a non-resonant (trans-1,2-bis(4-pyridyl)ethylene) molecule as well as a self-assembled monolayer (1-decanethiol). Small, low-cost sensors are in demand for a variety of applications, and SERS is positioned to contribute significantly with its remarkable sensitivity and molecular specificity.Key words: Raman, SERS, fiber-optics, sensor.