Miniaturized Laser Sources for Optical Neuroprostheses

描述(申请人提供)：红外神经刺激(INS)是一种新技术，有望增加神经假体中独立通道的数量。作为电刺激(ES)的补充技术，INS已被用于耳蜗、前庭系统、周围神经、脑和其他可兴奋组织，以提供精确靶向的、无伪影的神经刺激。这项拟议研究的长期目标是提高神经假体的性能。例如，人工耳蜗在恢复听力方面非常成功，但在嘈杂环境中的表现或使用者享受音乐的能力方面仍面临限制。这主要是由于数量有限。 由于电极之间的电串扰而产生的有效频率通道。西北大学和洛克希德·马丁公司已经证明了基于INS的神经假体的初步可行性和安全性，他们通过远程激光和光纤将光耦合到猫的耳蜗螺旋神经节。然而，INS的实际实施需要大量的小型化，而关键的缺失部分是可以集成到可植入设备中的光源。垂直腔面发射激光器(VCSEL)在提供所需的尺寸和性能组合方面前景看好。因此，第一期工程将确定VCSEL的可行性，以满足 光功率、功率效率和物理尺寸要求。第二阶段项目将开发适合植入的包装，并在动物身上进行有效性和安全性的概念验证演示。到目前为止，Vixar已经展示了最高功率的1860 nm VCSELs，但现状与INS的要求之间仍然存在差距。通过结合VCSEL的几个新设计特征，我们预计在芯片尺寸为0.25 mm x 0.25 mm x 0.125 mm的芯片中，每个通道的输出功率为50 mW，功率转换效率为&gt；25%。这些独创的设计特征包括外延层结构和掩膜特性的选择，这些特性提供了更好的电流捕获和限制以转换为光，优化的镜面结构允许更高的产生光发射效率，以及定制的接触和层掺杂特性以降低电阻。因此，该第一阶段项目将确定在INS中使用VCSEL设备的可行性，为第二阶段项目奠定基础，该项目将解决热管理、封装和概念验证问题。 与公共健康相关：这项研究将开发一种小型化的红外激光器，它将构成基于光刺激的神经假体的基础，具有显著提高的空间选择性。该装置的大小、功率和效率将使可植入装置成为可能，从而克服基于电刺激装置的一些问题，例如限制选择特定神经的能力的电流扩散，或限制人工耳蜗植入物中独立通道的数量。在人工耳蜗的例子中，这一创新将提高植入物的质量，特别是在嘈杂的环境中或在欣赏音乐方面。

DESCRIPTION (provided by applicant): Infrared neural stimulation (INS) is a novel technology that holds promise for increasing the number of independent channels in neuroprostheses. A complementary technology to electrical stimulation (ES), INS has been used in the cochlea, vestibular system, peripheral nerve, brain, and other excitable tissues to provide precisely targeted, artifact-free, stimulation of nerves. The long term goal of the proposed research is to improve the performance of neural prostheses. For instance, cochlear implants have been very successful in restoring hearing, but still face limitations in terms of their performance in noisy environments or the ability of the user to enjoy music. This is primarily due to the limited number of effective frequency channels resulting from electrical cross-talk between electrodes. The preliminary feasibility and safety of neuroprostheses based upon INS has been demonstrated by Northwestern University and Lockheed Martin by coupling light into the cochlear spiral ganglion of cats with a remote laser and optical fibers. However, the practical implementation of INS requires substantial miniaturization, with the key missing piece being an optical source that can be incorporated into an implantable device. Vertical Cavity Surface Emitting Lasers (VCSELs) hold great promise for providing the combination of size and performance that are required. The Phase I project will therefore establish the feasibility of the VCSEL for meeting the optical power, power efficiency and physical size requirements. A Phase II project would develop suitable packaging for implantation and perform a proof-of concept demonstration of efficacy and safety in animals. Vixar has demonstrated the highest power 1860nm VCSELs to date, but a gap remains between the status and the requirements for INS. By combining several new design features of the VCSEL we expect to achieve a 50mW output power per channel, a power conversion efficiency of > 25 percent with short pulses, in a chip size of 0.25mm x 0.25mm x 0.125mm. These original design features include the choices of epitaxial layers structures and mask features that provide improved current capture and confinement for conversion to light, optimized mirror structure to allow for greater emission efficiency of generated light, and a tailored contact and layer doping profile to reduce electrical resistance. This Phase I project will therefore establish the feasibility of using a VCSEL device in INS, setting the stage for the Phase II project, which will address thermal management, packaging and the proof-of concept. PUBLIC HEALTH RELEVANCE: This research will develop a miniaturized IR laser that will form the basis of optical stimulation based neuroprostheses, with dramatically improved spatial selectivity. The size, power and efficiency of the device would make possible implantable devices which overcome some of the issues of electrically based stimulation devices, for instance current spreading that limits the ability to select a particular nerve, or limits the numbr of independent channels in cochlear implants. In the example of cochlear implants, this innovation would improve the quality of the implants, particularly in noisy environments or in appreciating music.