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The key challenges in achieving this are multi-fold: delivering greater than a watt of power across the room, minimizing the exposure of the resulting high-power lasers to human tissue, and finally ensuring that the design meets the form-factor requirements of a smartphone and requires minimal instrumentation to the environment. This paper presents a novel, and to the best of our knowledge, the first design, implementation and evaluation of an end-to-end power delivery system that satisfies all the above requirements. Our results show that we can deliver more than 2 W at ranges of 4.3 m and 12.2 m for a smartphone (25 cm2) and table-top form factor (100 cm2) receiver respectively. Further, extensive characterization of our safety system shows that we can turn off our laser source much before a human moving at a maximum speed of 44 m\/s can even enter the high-power laser beam area.<\/jats:p>","DOI":"10.1145\/3161163","type":"journal-article","created":{"date-parts":[[2018,1,9]],"date-time":"2018-01-09T13:26:11Z","timestamp":1515504371000},"page":"1-21","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":64,"title":["Charging a Smartphone Across a Room Using Lasers"],"prefix":"10.1145","volume":"1","author":[{"given":"Vikram","family":"Iyer","sequence":"first","affiliation":[{"name":"University of Washington, Seattle, WA, USA"}]},{"given":"Elyas","family":"Bayati","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, WA, USA"}]},{"given":"Rajalakshmi","family":"Nandakumar","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, WA, USA"}]},{"given":"Arka","family":"Majumdar","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, WA, USA"}]},{"given":"Shyamnath","family":"Gollakota","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, WA, USA"}]}],"member":"320","published-online":{"date-parts":[[2018,1,8]]},"reference":[{"key":"e_1_2_1_1_1","doi-asserted-by":"publisher","DOI":"10.1109\/IROS.2011.6094731"},{"key":"e_1_2_1_2_1","unstructured":"Adafruit. 2017. 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