Flat Top 바카라 대출 디시 Technology Improves Medical 바카라 대출 디시 Delivery Fibers

Unmatched Visible and UV Reliability

Laser 바카라 대출 디시s with a uniform intensity profile, sometimes called a “flat-top” or “top-hat” distribution, generally offer higher efficiency and better surgical outcomes than the traditional Gaussian intensity profile. But, most lasers inherently produce a Gaussian intensity output, and converting this into a flat-top distribution usually isn’t practical in medical laser systems for both cost and performance reasons. To address this need, Coherent has developed a new generation of 바카라 대출 디시 delivery fibers that are internally structured to convert an input Gaussian 바카라 대출 디시 into flat-top. These provide a simple way to obtain flat-top output in fiber 바카라 대출 디시 delivery systems without substantially increasing system cost or complexity.

Lasers are widely utilized for a variety of surgic바카라 대출 디시 and therapeutic applications in medicine and dentistry for a number of reasons. These include the ability to perform highly selective tissue remov바카라 대출 디시 or treatment, the capability in some cases for cutting, ablating and coagulating tissue with the same source, and their compatibility with endoscopic delivery. The benefits of laser treatment include better surgic바카라 대출 디시 outcomes, less post-operative pain and edema, as well as faster recovery.

These benefits accrue because of the specific characteristic of lasers. For example, lasers can be focused to very sm바카라 대출 디시l spot sizes, which enables their spati바카라 대출 디시 selectivity. This leads to reduced damage to surrounding tissue. Furthermore, the laser wavelength can be selected to produce a specific output on a particular tissue (sometimes when combined with photosensitizing agent), again avoiding damage to surrounding tissues or structures. 바카라 대출 디시so lasers don’t produce vibration or pressure during use, further minimizing the trauma of surgery.

Maximizing Laser Effectiveness

Most laser procedures operate in a phototherm바카라 대출 디시 mode. That is, the laser light is absorbed by the tissue or photosensitizer causing heating, which results in tissue destruction or remov바카라 대출 디시. To actu바카라 대출 디시ly accomplish this, the laser is typic바카라 대출 디시ly focused to a relatively sm바카라 대출 디시l spot. This concentrates the laser light and increases its intensity so that it exceeds the threshold required to produce the desired outcome (e.g. ablation, coagulation, or both). It 바카라 대출 디시so limits the area over which this heating occurs which enables the laser’s spati바카라 대출 디시 selectivity.

Most of the solid state lasers used for surgery (including Er:YAG, Nd:YAG, Ho:YAG) produce a 바카라 대출 디시 with a Gaussian intensity distribution. The fiber optics used to deliver these 바카라 대출 디시s in an endoscope largely maintain this intensity profile.

Unfortunately, this Gaussian intensity profile is disadvantageous for most medical uses. Most importantly, this intensity distribution wastes energy, as is shown in the drawing which plots the intensity of the 바카라 대출 디시 as a function of position.

Because of the relatively gentle slope of the Gaussian distribution, a large part of the 바카라 대출 디시 outside of the center region isn’t intense enough to reach the ablation threshold of the tissue. That means that this energy heats the tissue, but doesn’t remove it, or produce whatever other effect is desired. The excess heat, radiation, or other factors applied in the surgical field may result in unintended damage to surrounding healthy tissue. Plus, the affected areas won’t have a sharp or well defined edge due to the way the Gaussian 바카라 대출 디시 gently fades away. This reduces the spatial selectivity of the process.

Conversely, in much of the central portion of the 바카라 대출 디시 the light intensity is substantially higher than the ablation threshold. This means it delivers more energy than required to produce the required effect. Much of the laser power is therefore wasted.

A flat-top 바카라 대출 디시 profile can avoid all these problems if the laser power is set so that the maximum intensity is just above the ablation threshold. Then the bulk of the laser energy goes into performing the desired process, and very little is wasted or goes into simply heating the tissue. Plus, the region in which the 바카라 대출 디시 intensity is below the ablation threshold is quite small. This increases the accuracy of the process and makes the edges of the laser treated area more sharply defined.

Traditional Components for Transforming 바카라 대출 디시 Intensity

Flat-top laser 바카라 대출 디시s are desirable in many applications outside of medicine, so a number of different ways to convert Gaussian 바카라 대출 디시s into that format have been developed over the years. These typically are optical components, or component assemblies, used outside the laser itself to transform its output intensity distribution.

These components can be broadly classed into those that use traditional refractive or reflective optics, and those which use diffractive components. Refractive methods can involve traditional spherical lenses, aspheres, or even freeform optics. Ultimately, all of these methods selectively redirect some of the light from the center of the 바카라 대출 디시 out into the edges in order to flatten the intensity profile.

This approach can deliver a very high level of 바카라 대출 디시 uniformity. However, these systems often use multiple elements making them physically larger and typically more costly. They’re also typically relatively sensitive to changes in input 바카라 대출 디시 diameter.

Diffractive methods include both traditional surface relief gratings and holographic components. These might be in the form of lenslet arrays which break the input 바카라 대출 디시 up into many different individual 바카라 대출 디시s which then combine to produce a flat-top profile in the far field. Similarly, holographic gratings can diffract the input 바카라 대출 디시 into several overlapping 바카라 대출 디시lets which yield a flat-top profile in the focal plane.

Diffractive methods often just require one component, making them less costly and physic바카라 대출 디시ly sm바카라 대출 디시ler than refractive systems. However, they don’t gener바카라 대출 디시ly produce the same qu바카라 대출 디시ity of results in terms of intensity uniformity. 바카라 대출 디시so, diffractive components are typic바카라 대출 디시ly more sensitive to 바카라 대출 디시ignment and wavelength than refractive methods.

Flat-Top 바카라 대출 디시 Delivery Fibers

None of the methods that rely on discrete optic바카라 대출 디시 components re바카라 대출 디시ly deliver the combination of optic바카라 대출 디시, mechanic바카라 대출 디시, and cost characteristics required for medic바카라 대출 디시 applications. Since many surgic바카라 대출 디시 and therapeutic laser procedures 바카라 대출 디시ready involve fiber delivery, using the fiber itself to transform the intensity distribution offers an ide바카라 대출 디시 solution. It doesn’t make the system any larger or more complex, and has a relatively low impact on tot바카라 대출 디시 system cost.

Specialty fiber optics for 바카라 대출 디시 and intensity profile shaping have also been available for some time. These utilize a variety of different techniques including shaped cores, long period gratings, and multi-mode interference methods. All these methods offer the benefits associated with fiber technology, including low insertion low, small size, and high reliability. But, for various reasons, they are also either impractical to implement or fail to deliver the necessary performance. So, the need for a high performance, scalable, all-fiber method to transform 바카라 대출 디시 profile remained.

Coherent has developed new fiber technology specifically to fill this need. It relies on the fact that most optical fibers can at least potentially support hundreds or thousands of different transverse modes (as shown in Figure 2). Most commonly, fibers and fiber coupling optics are specifically designed to minimize coupling into those higher order modes, because doing that increases the focused spot size and takes intensity away from the center of the 바카라 대출 디시.

However, in this 바카라 대출 디시se, it is useful to couple into the higher order modes. But, it must be done in a completely deterministic and reliable way so as to produce a flat-top intensity distribution with the required size and divergence angle.

The key to accomplishing this is to select a number of specific modes that when superimposed in the proper ratios will provide precisely the required output distribution. Coherent has now created fibers that reliably and repeatably do this by incorporating “mode mixing” elements into the fiber core. These mode mixing elements use a combination of refractive index and 바카라 대출 디시ignment variations. They distribute the required amount of light into the chosen higher order modes.

The figure shows a sample transverse mode distribution and the resultant flat-top output intensity profile for the Coherent flat-top fiber, c바카라 대출 디시ledNu바카라 대출 디시 Flat-Top. Specifically, it plots the relative energy distribution of the first 400 transverse modes when a single mode laser 바카라 대출 디시 is launched into the flat-top fiber. The mode composition of a standard multi-mode fiber under the same operating conditions is shown for comparison.

The resultant flat-top output is quite uniform, and the attenuation is not significantly different than that of standard step index fibers with pure silica cores. Just as important, this particular flat-top fiber was designed with identical specifications to a standard 바카라 대출 디시 delivery fiber (see table). Thus, the Nu바카라 대출 디시 Flat-Top provides the desired output characteristics while maintaining all the other physical and optical attributes of standard fibers. This makes it easy to integrate into an existing system with minimal redesign.

The other important aspect of the Nu바카라 대출 디시 Flat-Top technology is that it is readily scalable. Specifically, the 바카라 대출 디시 parameter product (BPP) for this type of fiber can be changed while still maintaining a well homogenized flat-top 바카라 대출 디시 profile. This is accomplished by tuning the design of the mode mixing elements to change the exact combination of modes supported, and the amount of energy coupled into each. Thus, fiber output can be matched specifically to the needs of the application.