What was the revenue generated by Lumentum's telecom and datacom products in the first quarter of 2020 
n demand for telecom transmission products after a lengthy period of telecom transport strength. Sales of chips to transceiver customers grew 13% sequentially to a new record level. We have strong engagement from new and existing customers for chips including for 5G wireless network applications. Based on the continued strong growth expected in global network and datacenter traffic, an optical infrastructure needed to support by 5G wireless networks.
We believe the market for our telecom and datacom products should be strong on a multi-year basis. We are well-positioned with our industry-leading products and deep customer relationships. We believe from global bandwidth expansion regardless of who builds or supplies networks. Our next generation products are critical to our global customer base and include high-performance DML, EML and pixel products enabling high speed optical transceivers including 400G and above and next generation wireless front hall and access solutions.
M-by-N and high port count twin ROADMs. A range of high-performance DCO transmission modules and underlying highly integrated components. And finally, high baud rate indium phosphide components including those for 800 gigabit transmission. Looking to the second quarter, we expect telecom and datacom revenue will be up sequentially given primarily by growth in telecom transmission and transceiver chip sales.
Now on to lasers. First-quarter laser demands softened more than projected due to elevated customer inventory levels, resulting in revenue dipping to $33.8 million. Looking to the second quarter, we expect lasers to rebound to the mid to low $40 million level. Over the long run because of our investments in unique new product and technologies, we believe we have good opportunities for growth driven by new laser product introductions in addition to market growth.
Our commercial lasers business is important to our long-term strategy. It provides us with significant addressable market to grow into and provides us with a level of customer and end market diversification. Throughout my remarks, I've highlighted the significant progress we have made toward our strategic and financial goals. Over the past several years, we have made significant investments in new products, markets, design wins and M&A.
We believe these investments position as well for the future. At Lumentum, we are releasing the power of light to create a brighter future and it is a very exciting time for all of our stakeholders. I would especially like to thank our employees for their hard work that has put us in such a great position. I will now hand it over to Wajid.
Wajid Ali -- Chief Financial Officer
Thank you, Alan. Good morning, everyone. I'm pleased to be discussing our strong first-quarter results. Net revenue for the first quarter was 449.9 million which was up 11% sequentially and 27% year on year.
GAAP gross margin for the first quarter was 37.3%. GAAP operating margin was 13.3% and GAAP diluted net income per share was $0.61. Again, GAAP results include the impact of restructuring, writedowns, amortization of intangibles and other charges related to the acquisition and our actions to attain acquisition synergies. First-quarter non-GAAP gross margin was 45.8% which was up 690 basis points sequentially and 550 points year on year.
As Alan noted, the strong year-on-year gross margin improvement was helped by improvements in telecomand datacom margins, as well as acquisition synergies. Non-GAAP operating margin for the first quarter was 27.3% which was up 830 points sequentially and 340 basis points year on year, driven by higher gross margins. Non-GAAP operating expenses totaled $83.3 million or 18.5% of revenue. SG&A expense was $37 million, R&D expense was $46.3 million.
Non-GAAP net income was a $111.4 million for the first quarter and includes $2.6 million of net interest expense and tax expense of $8.7 million. Non-GAAP diluted net income per share was a $1.44 based on a fully diluted share count of $77.6 million. We ended the quarter with cash and short-term investments 
n demand for telecom transmission products after a lengthy period of telecom transport strength. Sales of chips to transceiver customers grew 13% sequentially to a new record level. We have strong engagement from new and existing customers for chips including for 5G wireless network applications. Based on the continued strong growth expected in global network and datacenter traffic, an optical infrastructure needed to support by 5G wireless networks.
We believe the market for our telecom and datacom products should be strong on a multi-year basis. We are well-positioned with our industry-leading products and deep customer relationships. We believe from global bandwidth expansion regardless of who builds or supplies networks. Our next generation products are critical to our global customer base and include high-performance DML, EML and pixel products enabling high speed optical transceivers including 400G and above and next generation wireless front hall and access solutions.
M-by-N and high port count twin ROADMs. A range of high-performance DCO transmission modules and underlying highly integrated components. And finally, high baud rate indium phosphide components including those for 800 gigabit transmission. Looking to the second quarter, we expect telecom and datacom revenue will be up sequentially given primarily by growth in telecom transmission and transceiver chip sales.
Now on to lasers. First-quarter laser demands softened more than projected due to elevated customer inventory levels, resulting in revenue dipping to $33.8 million. Looking to the second quarter, we expect lasers to rebound to the mid to low $40 million level. Over the long run because of our investments in unique new product and technologies, we believe we have good opportunities for growth driven by new laser product introductions in addition to market growth.
Our commercial lasers business is important to our long-term strategy. It provides us with significant addressable market to grow into and provides us with a level of customer and end market diversification. Throughout my remarks, I've highlighted the significant progress we have made toward our strategic and financial goals. Over the past several years, we have made significant investments in new products, markets, design wins and M&A.
We believe these investments position as well for the future. At Lumentum, we are releasing the power of light to create a brighter future and it is a very exciting time for all of our stakeholders. I would especially like to thank our employees for their hard work that has put us in such a great position. I will now hand it over to Wajid.
Wajid Ali -- Chief Financial Officer
 Thank you, Alan. Good morning, everyone. I'm pleased to be discussing our strong first-quarter results. Net revenue for the first quarter was 449.9 million which was up 11% sequentially and 27% year on year.
GAAP gross margin for the first quarter was 37.3%. GAAP operating margin was 13.3% and GAAP diluted net income per share was $0.61. Again, GAAP results include the impact of restructuring, writedowns, amortization of intangibles and other charges related to the acquisition and our actions to attain acquisition synergies. First-quarter non-GAAP gross margin was 45.8% which was up 690 basis points sequentially and 550 points year on year.
As Alan noted, the strong year-on-year gross margin improvement was helped by improvements in telecomand datacom margins, as well as acquisition synergies. Non-GAAP operating margin for the first quarter was 27.3% which was up 830 points sequentially and 340 basis points year on year, driven by higher gross margins. Non-GAAP operating expenses totaled $83.3 million or 18.5% of revenue. SG&A expense was $37 million, R&D expense was $46.3 million.
Non-GAAP net income was a $111.4 million for the first quarter and includes $2.6 million of net interest expense and tax expense of $8.7 million. Non-GAAP diluted net income per share was a $1.44 based on a fully diluted share count of $77.6 million. We ended the quarter with cash and short-term investments 